intermittent error in asp.net

Hi

I have run into a really bizzare problem in that asp.net stops working
intermittently - and I can only get it to restart after restarting my
computer.

My environment is Windows XP Pro SP2, running asp.net 1.0, asp.net 1.1 and
asp.net 2.0. All of my asp.net applications are running on asp.net 1.1
(v1.1.4322)

When problems occurs with asp.net, an ASP.NET related application will
return the following in browser

Server Application Unavailable
The web application you are attempting to access on this web server is
currently unavailable. Please hit the "Refresh" button in your web browser
to retry your request.

Administrator Note: An error message detailing the cause of this specific
request failure can be found in the application event log of the web server.
Please review this log entry to discover what caused this error to occur.


In the application event log, the following is logged.

aspnet_wp.exe could not be started. The error code for the failure is
80004005. This error can be caused when the worker process account has
insufficient rights to read the .NET Framework files. Please ensure that the
..NET Framework is correctly installed and that the ACLs on the installation
directory allow access to the configured account.


Process Model of machine.config has administrator account already configured
(it must have been configured correctly as everything works if I shut down
and restart).

This problem only started recently and I am at a total loss as to what could
be the issue. The administrator account has log-on-as-service privilege and
I have event granted administrator access to IWAM_Machine account as well
(which I don't believe should be necessary).

All help is appreciated.

CW