Assemblies that use to download by IE (Smart client) stop to download suddenly.

We use IE & CLR build in MIME filter to download .NET assembly from remote server into GAC and run those assemblies. It works great until one day on several machines we start to receive errors regarding the download assemblies.

Using Filemon, Regmon and IEHost debug log we discover that MIME filter isn't call for some reason. There isn’t any sign to mscoree.dll if filemon and IEHost log is empty. Farther investigation, that based on comparing working machine registry to non working registry, found out that there are missing registry entries in the non functional machine (such as "Cor MINE Filter").

We didn’t success to find out what is the exact reason (maybe SP update ?) . I'll be glad if someone can supply any information.

Right now, the only way we found out to fix this issue is by fixing CLR (reinstalling).