2.9 file uploade issue

I upgraded from 2.8.2 to 2.9.  

After adding a file and hitting the "Upload" button I get the following pop-up:

An error occured:
Method not found: 'Void System.Web.HttpWorkerRequest.SendCalculatedContentLength(Int64)'.

When I click "OK" on the pop-up the upload completes.

Can you please let me know the  IIS and ASP.NET versions.

It may be related to whether Microsoft .NET Framework 2.0 Service Pack 1 is installed or not.

ASP.net 2.0.50727
IIS 5.0

I reapplied SP1 for the .NET Framework and it appears to have fixed this problem.