Might be related - I made a forum post yesterday, and when I did, I noticed the time was in GMT.
I went into my account and changed my timezone so that forum posts showed my local time.
I have tried numerous time to Synchronize time on my iphone. I updated the last IOS update (Iphone 4s) and I got an error along the lines of "invalid time format"
Synchronizing time again worked ok.
Still can't login.
I haven't made any changes to my time zone settings ..
Also the client/ server time shift according to the app is 0 ( which is how it should be i'm guessing ) ... and it seems to be measured in seconds ..