monkeybrains, I'm sorry you are having trouble staying logged into PC. Unfortunately, I'm not enough tech savvy to give you any hope or answers as to help your situation, but I do hope you can find a way to work around the problem and not leave PC.
If you find it kicks you off when you are answering a post or writing a pm, I can suggest that you type it out in notepad or something like that and copy/paste it onto PC when you know you are logged in so you can send it. I hope that helps at least a little bit.