I've come across an error with SP2010 standard search a few times now. The error message is "Illegal operation attempted on a registry key that has been marked for deletion",
and it happens when "SearchService.svc" is accessed by SP Search. I have seen this error on my dev environment, test environment and a client's UAT environment. The resolution is a reboot of the server, but that's obviously far from ideal.
I've tried to restart all SharePoint related services too without any luck. This error doesn't seem to occur regularly, and can take days before it happens after a reboot.
The full error message is below:
Server Error in '/4ca4d32e32d848338cab8aeeb78f7a2b' Application.