I suspect this is the key here and it has to do with the online services potentially spitting out gibberish and causing performance issues on the client side as it repeats requests for data and slows the sim down in the process.
Online services have been horribly bad for many folks since mid-April or so. I have good days, and I have bad days. No updates, new software, etc. And no amount of reboots fixes it.
There have been lots of reports in this thread, but nothing seems to ahve been done about it yet. It just seems to get worse with time.