Jason, thanks for your reply.
I'm afraid I have already done that deletion. It's a real pain having to do this each and every time i install a web assist extension but i've accepted it as the price of using WA products. i imagine it's mainly a adobe error but someone needs to get a fix in!
the only solution i've ever found is a complete uninstall of DW and then reinstall of the main program and all extensions.
with over 500 web sites and about 70 active sites and 10 or so in development at any one time that is a major task. and that's not even counting in the extension manager work.
so once again as these forums can present no sensible solution i am going to go thru the above process.
while i've a number of WA packages i cannot afford the downtime each installation or upgrade demands. so (in addition to the loss of asp versions) i've not taken up any of the latest offers. loosing 2 or 3 days due to these sort of errors is simply unacceptable. while i know very well that you are not personally responsible for WA coding i wonder who is taking responsibility for such an unprofessional solution such as 'delete WinFileCache.dat'!