Further trial and error shows systematic crash upon trying to scan m4a files:

$ picard 
/var/lib/python-support/python2.6/picard/webservice.py:25: DeprecationWarning: the md5 module is deprecated; use hashlib instead
  import md5
/var/lib/python-support/python2.6/picard/webservice.py:28: DeprecationWarning: the sha module is deprecated; use the hashlib module instead
  import sha
[mp3 @ 0xb43355c0]mdb:403, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:403, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:403, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:403, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:511, lastbuf:382 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:511, lastbuf:382 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:408, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:408, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:408, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:408, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:511, lastbuf:382 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:511, lastbuf:382 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:404, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:404, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:404, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:404, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:511, lastbuf:382 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:511, lastbuf:382 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:409, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:409, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:409, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:409, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:511, lastbuf:382 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:511, lastbuf:382 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:403, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:403, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:403, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:403, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:511, lastbuf:382 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:511, lastbuf:382 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:406, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:406, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:406, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:406, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:511, lastbuf:382 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb43355c0]mdb:511, lastbuf:382 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb432faf0]mdb:410, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb432faf0]mdb:410, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb432faf0]mdb:410, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb432faf0]mdb:410, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb432faf0]mdb:511, lastbuf:382 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb432faf0]mdb:511, lastbuf:382 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:403, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:403, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:403, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:403, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:511, lastbuf:382 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:511, lastbuf:382 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:404, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:404, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:404, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:404, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:511, lastbuf:382 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:511, lastbuf:382 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:409, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:409, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:409, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:409, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:511, lastbuf:382 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:511, lastbuf:382 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:404, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:404, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:404, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:404, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:511, lastbuf:382 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:511, lastbuf:382 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:406, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:406, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:406, lastbuf:0 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:406, lastbuf:0 skipping granule 1
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:511, lastbuf:382 skipping granule 0
    Last message repeated 1 times
[mp3 @ 0xb4322f60]mdb:511, lastbuf:382 skipping granule 1
Segmentation fault