Global, Help, Trade, Whisper tabs keep dissapearing

These tabs disappear continuously in my browser. I cannot talk on the Global window, but for example, if I have the trade window open even if the trade tab disappears the list stays on. Please give me an idea of what can I do

Clearing the cache did not do anything good

Thanks

P.S. I'm using Google Chrome, updated, on a WinXP64 bit OS

I've heard of this problem before relating to Flash in Windows 7. If I recall, running Flash in 32-bit mode solves it.

Someone else may have a clearer answer because I don't use Windows 7.