How did that happen, I thought I upgraded properly. I've also been sending and receiving coins without a problem.
I can only speak for myself, it usually happens to me when i force quit the client or if I run it under different permissions. I should note I'm using OS X. Redownloading the blockchain fixes it.
Just finished downloading it again after I deleted it. Then repalced the .dat file with my backed-up one. It seems to be good now, thanks