I've searched high and low for the answer to this cubase problem...any help would be great.

I'm using cubase vst/24, version r2 (latest update) and Seasound solo sound card (1.3.1 drivers) on an IDE g-4, 350mhz, 256 mb RAM.
I was using system 8.6 and recently changed to 9.0.4, but the problem is roughly the same on both (although worse on 9.0.4).

Basically what happens is the sound will randomly stop. The cursor keeps moving, but sound will stop coming out. This coincides with the performance meter (it will be at the max position for the CPU reading when the sound quits). This happens more often when there's more tracks and effects put on, but it's happened with as few as 5 tracks 45 seconds long with only a couple of effects.
I've tried everything that people have suggested, including (but not lilmited to)
trying every buffer size,
allocating more (and less) memory to the program.
Doing a clean install of the os.
Reinstalling Cubase.
trashing the preferences.
running norton & defragging drive,
zapping pram,
rebuilding desktop,
running disk warrior,
running base extensions & Cubase extensions only. (which included disabling any software running in the background).
I've spent more money with calls to Steinberg in California then the program actually costs. I've also talked extensively to Seasound and the problem doesn't seem to be there. I'm pretty much ready to buy new software at this point, but I'm still looking for a solution.
I'd be thankful for any feedback...or if you know anyone who would know.

OS 8.6 HAS BEEN SOLID FOR ME WITH A G3 400 WITH SCSI DRIVES, 384 RAM. OS 9 LEANS TOWARD MORE INTERNET FEATURES AND I DON'T KNOW OTHER CUBASE, PTOOLS PEOPLE WHO HAVE RISKED THE NEW OS WHEN 8.6 CAN BE MADE ROCK SOLID. IN CUBASE, YOU MIGHT WANT TO TRY MAKING A COPY OF SESSION AND BACKING OFF ALL FX AND WATCH CPU METER AS YOU ADD THEM BACK INDIVIVDUALLY. BE CERTAIN ALL MIDI IS MUTED. IF CPU METER STILL GETS NEAR PEAKING, MAYBE TRY NO FX AND BOUNCE TRACKS TO MIMUMIZE # OF TRACKS AND FX. MONITOR CPU METER, AND BUILD BACK UP. I USE THE PTOOLS AM 111 CARD , IF CPU METER NEAR PEAKS, SHE'LL CUT OUT TO DEFAULT APPLE SOUND. WHEN I'M WORKING IN AUDIO ONLY, I SHUT DOWN ALL MIDI INFO. ALSO, I'VE HAD CUT OUTS BECAUSE OF MULTIPLE USB HOOK-UPS AND REDUCE THESE TO ONLY COMPUTER KEYBOARD AND MIDI INTERFACE.
SAVE OFTEN, AND OCCASSIONALLY CLOSE SESSION COMPLETELY, OPEN AGAIN AND SAVE. IF ANY OF THIS MAKES THE FREEZE LESS FREQUENT, THEN WORK THE HELL OUT OF YOUR COPY SESSION UNTIL IT FREEZES AGIN, REMEMBER EXACTLY THE PRECEDING COMMAND THAT CONFUSED THE PROGRAM AND YOU'LL PROBABLY WIDDLE IT DOWN. MULTIPLE FX, INSERTS AND EQ IS ALOT OF DEMAND, MAYBE BOUNCE 4 OR 6 TRKS WITH FX TO 2(KEEP ORIG 4 OR 6 SOMEWHERE OUT OF SESSION) AND WATCH HOW LITTLE WORK THE CPU HAS TO DO. GOOD LUCK, WE ALL KNOW THE FRUSTRATION, MY OLD POWERMAC 7300, 200MHZ CAN STILL BE HAMMERED AND SLAMMED THROUGH MULTIPLE SESSIONS IN PTOOLS AND CUBASE AND NOT MISS A TICK. BOTH THESE COMPUTERS ARE DEDICATED TO AUDIO SO ALL PRINT, TELE, ETC. APPS, EXTENSIONS, DRIVERS ARE TRASHED. AGAIN, PATIENCE AND GOOD LUCK.