upload problem

When i upload file, the follow error occurred:

Method not found 'Void System.Web.HttpWorkerRequest.SendCalculatedContentLength(Int64)'

how can i solve this problem?

Please apply Microsoft .NET Framework 2.0 Service Pack 1 to fix this problem.

Thanks for your reply. 
I applied .net 2.0 SP1, but it still has problem some time. The popup says has error but error message is blank. When click OK button, the file actually uploaded.

No, the blank error is another error so the previous error is fixed.

It seems you downloaded v2.9 on the first day of its release, only that build was causing the blank error so you need to download the revised build. I have sent you the download link via email.