audio recording out of sync (and getting worse!)

[r0cker]

hello, thanks for reading this, i have a bit of a problem with cubase 5. after i have recorded audio that is playing perfectly in time into the computer, it appears (and plays back) out of time. as the audio track progresses the notes get increasingly out of time with gaps between them getting larger and larger. when the audio plays back the notes appear out of time and i can cut the wav file up and then put the notes in time and there are no problems but when i record into cubase the wav gets increasingly out of time. i am sure the notes are perfectly in time as i am triggering them from cubase. i have also messed around with most of the asio settings but still no joy. if anyone could help i would be really grateful as this is causing me a real headache!

my set up is:

800 mhz athlon
320 mb ram
turtle beach pinnacle sound card

please let me know if you need any additional info.
thanks in advance,
r0cker