At the end of 2011, we started having issues with some of our units in some areas of Sweden.
The affected units all had Firmware 6.63c, while units with 7.2a, 7.44 and 7.46 was unaffected.
Today I got word from the operator that “the terminals were not compatible with the QoS setting that was set by the network” (or something like that).
The operator has fixed this on their side now. 
I’m wondering if it’s a known issue that was fixed in later firmware releases or if newer firmware is unaffected for other reasons.
The symptoms reminded of the issue described in https://forum.sierrawireless.com/t/gprs-roaming/5276/1
What was different is that there was no roaming in the current case, but we still got +CME ERROR: 3 when trying to activate the PDP context.