IIS 7.5, MVC3, corrupted URLs

We have an issue with one of our web servers where the URL gets jumbled occasionally resulting in a Http Exception. The URLs have a corrupted string appended to every request /(sdfkljsdlfjrwlojflksdjfssdfdsfsdlkjsdgnmldigkh324sdlkjsdgdfsdf90sdfnsdfsdf)/_Layout.html and exception says...'could not be found'. Doing an IIS reset resolves this issue on the web server. But we get this issue again later after a few months and this happens only on one web server. We use IIS7.5, .NET Framework 4.0, ASP.NET MVC3 and an F5 Load Balancer.

Any help would be appreciated.

Thank you,

Kumar