Framework Corruption

"BC32400: Class 'CLSID_CorSymWriter' could not be created: Access is denied."

This is the error we get while trying to run our .NET application.
The application is a ASP.net/VB.net website running on MS SQL Server DB. It runs a host of windows services like MS Excel and MS Project.
This error has been occurring since yesterday evening 7 pm and so far a lot of diagnostics have gone into it,with us doing overtime late into night :)

As far as obtained from the internet, the .net framework requires reinstallation. Based on logs,we have been able to find the service which might have caused a registry corruption leading to this.
We have already run various tests and diagnostics to isolate and fix the issue without opting for tough solutions like re-formatting.

After spending many hours in front of our server in the closed and otherwise inaccessible server room, the decision has been taken to format the server. This is due to application's criticality to the day-to-day working of the organization.
But I have asked the team to record all logs and keep for further study. Hopefully we can make a learning out of it for future cases.