Canoscan suddenly fails to initialise

The following problem has ONLY surfaced since I uninstalled NAV & NIS and installed Zone Alarm and Avast... (but of course this may be unrelated)

When I try to open Canoscan I get the following message:

The application failed to initialise properly (0xc0000142)

And when I put the original disc in to reinstall it I get the following message:

C:\progra~1\symantec\S32EVNT1.dll
An uninstallable Virtual Device Drive failed Dll initialization

The choice then is to either CLOSE or IGNORE

If I chose IGNORE I get the following message:
C:\Windows\Sys32\Autoexec.NT.
The system file is not suitable for running MS-DOS and Microsoft Applications...

Now to my knowledge I have done NOTHING else to my comp...... (AS in install or uninstall anything else....)

And so far the canoscan program seems to be the only one affected

( I use it at least a few times per week)

Any ideas???

Thanks in advance you wonderful Geeks...

Cheers
Wendy

 

Please????
Anyone???