I used to have problems on Ubuntu and derived distros from 1-3 years ago, but currently use the latest 64bit Ubuntu at home and it works fine and setup a few at work and they work well as well, much more stable then the last time I tried it.
Just a side note, IMO you really shouldn't be using POP for emails, the only reason to would be if that is all your mail server supports, or you keep running out of space on your mail server.
64 bit. It was stable on Linux well before it was stable in the world of windows from my experience. This is from the home user point of view, I can't speak for the early 64 bit windows servers.
You'll be able to export everything into a PST then import that into whatever, PST is pretty much universally read by most\all modern day email clients.
Just picking up on this one, I think I might dig out a copy of Microsoft Outlook to install on my Windows PC, and do a copy from Live Mail into that.
I will then have a PST file, which will hopefully be recognised by Thunderbird... won't it?