Strangeest Logic Problem Ever, Won't play audio tracks in Platinum Options

[Ryanair]

This is the most bizzarre logic/mac problem ever, i've got a new mac G4 800 with 1.5Gig Ram, mac os9.2, delta-66 card/omni I/O, a midisprot 4x4 and AMT8. Everything was working perfectly for about 3 weeks, then i updated the drivers for the delta card to try and stop the errors i got upon booting logic, since then in logic platinum, if i start the program,(even without any preferences/autoload) and i import an audio file (any type) then drag and drop it onto the arrange, and start the sequencer, the audio files don't play at all, i don't even get a flicker on the level meter, it's like they're not even there! BUT if i double click on the audio file in the arrange window to see the waveform, and use the speaker button, it plays no problem, and i get a level reading on the mixer page/boarder of the arrange window. This problem is the same with Mac AV and the delta Asio.
I can record audio perfectly. (And the audio instruments, eg, EXS work fine.
If i start uplogic and record audio, then it plays back fine, but as soon as i import an audio file or bounce etc, the audio in the sequence will no longer play.

HOWEVER....

I've tryed a friends Logic Gold on my system, and everything works perfectly, it now seems to be just logic platinum,
but remember, everything was working fine when i first got the system,
Please can somebody help me, thanks.