Logic Pro 7 & earlier Logic 5.5.1 help needed - glitching!!

Hi chaps

Ive got a really urgent problem i need help with. I normally use Logic 9 on my macbook pro, but i have 2 old projects i desperately need to finish on my old PC v 5.5.1.

Up until a couple of months ago i have never had any issues with it, but now whenever i try to play the songs, they glitch in sort of stop/start manner. Ive reinstalled the soundcard (Delta 66), and that hasnt helped at all.

I sometimes get error messages like this (the sample rate is always different):

Error while trying to synchronizeAudio and MIDI. Sample rate 40846 recognized. Check conflict between Logic Platinum and external device.

Im running XP Professional and service Pack 2, by the way

Please help me if you can - i really need to get this projects finished and its so annoying as i am sure its something simple!

Thanks in advance,