Just wondering if anyone else has been having problems with FTB v. 5.1.

I'm running Win7, and I've had the program on this computer for about 2 years without any issues, but the last few weeks, I haven't been able to make changes to anyone's names, and when I resize the window, it gives me a "parameter is not within limits" error, and I had to click "ok" to get it to go back, but now it gives me the error, and it doesn't even say anything on the box that pops up, and I have to click "ok" about 6 times before it will go away.