Edirol Ua-5 And Logic, UA-5 crashing very frequently Options

[ThorD]

I've seen some positive views on the UA-5 in this forum,
as I myself have had nothing but trouble with it I am hoping
someone can share their experiences with me.

UA-5 crashing frequently

My new UA-5 crashes very frequently (every 10 minutes or so) irrespective of workload, and it also gets overloaded very quickly (ASIO error message after playback of only a dozen tracks, stereo and mono, 48 KHz 16-bit).

A number of seemingly innocent operations in Logic (save, rewind, plugin on/off, playback, record....) will result in losing sound, the soundcard neding rebooting and Logic restarting. A number of ASIO error messages will occasionally appear.

My setup is as follows:
Apple iMac G4 800 MHz 768 MB RAM running MacOS 9.2.2
Logic 4.8.1
Various plug-ins
FatMan 2 valve preamp
Midiman midisport running OMS 2

I am using the Edirol-provided ASIO 1 16 bit driver.
I run Advanced mode.
I tried downloading more recent drivers from the Edirol website, these crashed my machine
I have removed all potential extension conflicts on the Mac
I have allocated 256 MB memory to Logic
I have tried all possible setting combinations (buffer size, latency adjustment) in the Logic ASIO hardware window
I have ensured the UA-5 has its own dedicated USB drive.
Mac virtual memory, TCP/IP and Appletalk is switched is off

The UA-5 is heading for the dustbin soon if I can't sort this out - any advice is much appreciated.

ThorD