Ooh! Finally something I can help with.
Quick answer - try downloading the latest version of DirectX from
http://www.microsoft.com/windows/directx/default.aspx
Long answer - My POL was looking really pixelated and running really slow, and the game would give an error right after it went to full screen mode, so I called tech support. This was, of course, at a time when the servers were down, so I'm sure they had about 9999999999 other people calling, but I eventually got through.
The guy told me to open FFXI config, and asked me to change some setting in it. I opened it up, and it was blank o.o He told me that this is usually a sign that something's wrong with DirectX. I updated to 9.0, and after that, the config menu was back, POL ran fine, and the game didn't have any errors.
I don't know if you're having the other issues with POL or FFXI, but it's still probably worth a shot.
If that doesn't work, you might try updating your video card drivers... that's the other thing he told me to do.