So strangely, the camera has spontaneously started working for me again.  No reboot, no nothing.  Earlier, I was seeing the same kind of errors as Jono:

[51977.676130] 5:-1:4: cannot set freq 48000 to ep 0x86
[51977.680258] 5:-1:4: cannot set freq 48000 to ep 0x86
[51977.684611] 5:-1:4: cannot set freq 48000 to ep 0x86
[51977.688987] 5:-1:4: cannot set freq 48000 to ep 0x86
[51977.693848] 5:-1:4: cannot set freq 48000 to ep 0x86
<snip>
[51978.605699] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: -71 (exp. 2).
[51978.609799] 5:-1:4: cannot set freq 48000 to ep 0x86
[51978.613916] uvcvideo: Failed to set UVC probe control : -71 (exp. 26).
[51978.618030] 5:-1:4: cannot set freq 48000 to ep 0x86
[51978.622147] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: -71 (exp. 2).
[51978.626259] 5:-1:4: cannot set freq 48000 to ep 0x86
<snip>
[52035.239485] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: -71 
(exp. 2).
[52035.243607] uvcvideo: Failed to set UVC probe control : -71 (exp. 26).
[52035.247719] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: -71 (exp. 2).
[52035.251833] uvcvideo: Failed to query (GET_DEF) UVC control 3 on unit 2: -71 (exp. 2).
[52035.255946] uvcvideo: Failed to query (GET_DEF) UVC control 7 on unit 2: -71 (exp. 2).
[52035.260063] uvcvideo: Failed to query (GET_DEF) UVC control 11 on unit 2: -71 (exp. 1).
[52035.264176] uvcvideo: Failed to query (GET_DEF) UVC control 4 on unit 2: -71 (exp. 2).
[52035.268292] uvcvideo: Failed to query (GET_DEF) UVC control 5 on unit 2: -71 (exp. 1).
[52035.272412] uvcvideo: Failed to query (GET_CUR) UVC control 11 on unit 2: -71 (exp. 1).
[52035.276521] uvcvideo: Failed to query (GET_DEF) UVC control 8 on unit 2: -71 (exp. 2).
[52035.280635] uvcvideo: Failed to query (GET_DEF) UVC control 1 on unit 2: -71 (exp. 2).
[52035.284777] uvcvideo: Failed to set UVC probe control : -71 (exp. 26).
[52035.288863] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: -71 (exp. 2).
[52035.292997] uvcvideo: Failed to query (GET_DEF) UVC control 3 on unit 2: -71 (exp. 2).
[52035.297096] uvcvideo: Failed to query (GET_DEF) UVC control 7 on unit 2: -71 (exp. 2).
[52035.301208] uvcvideo: Failed to query (GET_DEF) UVC control 11 on unit 2: -71 (exp. 1).
[52035.305334] uvcvideo: Failed to query (GET_DEF) UVC control 4 on unit 2: -71 (exp. 2).
[52035.309697] uvcvideo: Failed to query (GET_DEF) UVC control 5 on unit 2: -71 (exp. 1).
[52035.313689] uvcvideo: Failed to query (GET_CUR) UVC control 11 on unit 2: -71 (exp. 1).
[52035.317811] uvcvideo: Failed to query (GET_DEF) UVC control 8 on unit 2: -71 (exp. 2).
[52035.321927] uvcvideo: Failed to query (GET_DEF) UVC control 1 on unit 2: -71 (exp. 2).
[52035.326038] uvcvideo: Failed to set UVC probe control : -71 (exp. 26).
[52035.330147] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: -71 (exp. 2).
[52035.334261] uvcvideo: Failed to query (GET_DEF) UVC control 3 on unit 2: -71 (exp. 2).
[52035.338379] uvcvideo: Failed to query (GET_DEF) UVC control 7 on unit 2: -71 (exp. 2).
[52035.342480] uvcvideo: Failed to query (GET_DEF) UVC control 11 on unit 2: -71 (exp. 1).
[52035.346596] uvcvideo: Failed to query (GET_DEF) UVC control 4 on unit 2: -71 (exp. 2).
[52035.350710] uvcvideo: Failed to query (GET_DEF) UVC control 5 on unit 2: -71 (exp. 1).
[52035.354820] uvcvideo: Failed to query (GET_CUR) UVC control 11 on unit 2: -71 (exp. 1).
[52035.358809] uvcvideo: Failed to query (GET_DEF) UVC control 8 on unit 2: -71 (exp. 2).
[52035.362941] uvcvideo: Failed to query (GET_DEF) UVC control 1 on unit 2: -71 (exp. 2).
[52056.209680] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: -71 (exp. 2).
[52056.215304] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: -71 (exp. 2).
[52056.219432] uvcvideo: Failed to set UVC probe control : -71 (exp. 26).
[52056.223649] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: -71 (exp. 2).
[52056.227763] uvcvideo: Failed to query (GET_DEF) UVC control 3 on unit 2: -71 (exp. 2).
[52056.231870] uvcvideo: Failed to query (GET_DEF) UVC control 7 on unit 2: -71 (exp. 2).
[52056.235984] uvcvideo: Failed to query (GET_DEF) UVC control 11 on unit 2: -71 (exp. 1).
[52056.240145] uvcvideo: Failed to query (GET_DEF) UVC control 4 on unit 2: -71 (exp. 2).
[52056.244223] uvcvideo: Failed to query (GET_DEF) UVC control 5 on unit 2: -71 (exp. 1).
[52056.248334] uvcvideo: Failed to query (GET_CUR) UVC control 11 on unit 2: -71 (exp. 1).
[52056.252445] uvcvideo: Failed to query (GET_DEF) UVC control 8 on unit 2: -71 (exp. 2).
[52056.256564] uvcvideo: Failed to query (GET_DEF) UVC control 1 on unit 2: -71 (exp. 2).
[52056.260678] uvcvideo: Failed to set UVC probe control : -71 (exp. 26).
[52056.264788] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: -71 (exp. 2).
[52056.268923] uvcvideo: Failed to query (GET_DEF) UVC control 3 on unit 2: -71 (exp. 2).
[52056.273046] uvcvideo: Failed to query (GET_DEF) UVC control 7 on unit 2: -71 (exp. 2).
[52056.277319] uvcvideo: Failed to query (GET_DEF) UVC control 11 on unit 2: -71 (exp. 1).
[52056.281384] uvcvideo: Failed to query (GET_DEF) UVC control 4 on unit 2: -71 (exp. 2).
[52056.285498] uvcvideo: Failed to query (GET_DEF) UVC control 5 on unit 2: -71 (exp. 1).
[52056.289609] uvcvideo: Failed to query (GET_CUR) UVC control 11 on unit 2: -71 (exp. 1).
[52056.293743] uvcvideo: Failed to query (GET_DEF) UVC control 8 on unit 2: -71 (exp. 2).
[52056.297835] uvcvideo: Failed to query (GET_DEF) UVC control 1 on unit 2: -71 (exp. 2).
[52056.301946] uvcvideo: Failed to set UVC probe control : -71 (exp. 26).
[52056.306055] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: -71 (exp. 2).
[52056.310197] uvcvideo: Failed to query (GET_DEF) UVC control 3 on unit 2: -71 (exp. 2).
[52056.314290] uvcvideo: Failed to query (GET_DEF) UVC control 7 on unit 2: -71 (exp. 2).
[52056.318405] uvcvideo: Failed to query (GET_DEF) UVC control 11 on unit 2: -71 (exp. 1).
[52056.322516] uvcvideo: Failed to query (GET_DEF) UVC control 4 on unit 2: -71 (exp. 2).
[52056.326661] uvcvideo: Failed to query (GET_DEF) UVC control 5 on unit 2: -71 (exp. 1).
[52056.330772] uvcvideo: Failed to query (GET_CUR) UVC control 11 on unit 2: -71 (exp. 1).
[52056.334874] uvcvideo: Failed to query (GET_DEF) UVC control 8 on unit 2: -71 (exp. 2).
[52056.338975] uvcvideo: Failed to query (GET_DEF) UVC control 1 on unit 2: -71 (exp. 2).
[52141.650676] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: -71 (exp. 2).
[52141.654797] uvcvideo: Failed to set UVC probe control : -71 (exp. 26).
[52141.658899] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: -71 (exp. 2).
[52141.663018] uvcvideo: Failed to query (GET_DEF) UVC control 3 on unit 2: -71 (exp. 2).
[52141.667144] uvcvideo: Failed to query (GET_DEF) UVC control 7 on unit 2: -71 (exp. 2).
[52141.671251] uvcvideo: Failed to query (GET_DEF) UVC control 11 on unit 2: -71 (exp. 1).
[52141.675390] uvcvideo: Failed to query (GET_DEF) UVC control 4 on unit 2: -71 (exp. 2).
[52141.679483] uvcvideo: Failed to query (GET_DEF) UVC control 5 on unit 2: -71 (exp. 1).
[52141.683586] uvcvideo: Failed to query (GET_CUR) UVC control 11 on unit 2: -71 (exp. 1).
[52141.687715] uvcvideo: Failed to query (GET_DEF) UVC control 8 on unit 2: -71 (exp. 2).
[52141.691853] uvcvideo: Failed to query (GET_DEF) UVC control 1 on unit 2: -71 (exp. 2).
[52141.695940] uvcvideo: Failed to set UVC probe control : -71 (exp. 26).
[52141.700065] uvcvideo: Failed to query (GET_DEF) UVC control 2 on unit 2: -71 (exp. 2).
[52141.704167] uvcvideo: Failed to query (GET_DEF) UVC control 3 on unit 2: -71 (exp. 2).
[52141.708306] uvcvideo: Failed to query (GET_DEF) UVC control 7 on unit 2: -71 (exp. 2).
[52141.712420] uvcvideo: Failed to query (GET_DEF) UVC control 11 on unit 2: -71 (exp. 1).
<snip>

But now, I get no errors and the camera works.