Interestingly I am experiencing the exact same symptoms. I am with Telstra Next G in Australia.
I have tried upgrading the firmware to the latest provider level (AC880U_Telstra_ F1_0_0_19ap.exe vs AC881U_F1_2_3_15ap.exe for AT&T - Note 880U is Australian version of 881U) but with no success.
Also note that umtsmon does not work for me either.
Interestingly I am experiencing the exact same symptoms. I am with Telstra Next G in Australia.
I have tried upgrading the firmware to the latest provider level (AC880U_Telstra_ F1_0_0_19ap.exe vs AC881U_ F1_2_3_ 15ap.exe for AT&T - Note 880U is Australian version of 881U) but with no success.
Also note that umtsmon does not work for me either.
Working perfectly under Windows.