Multiple RadUpload Control in One Page

Question

I have an aspx page that uses master page. In the papx page, I load a user control containing 2 RadUpload controls (Rad1 and Rad2). User can choose to upload the file either using the first RadUpload or the second RadUpload and there is certain validation applied for each RadUpload.

The weird thing happened is that when I upload file using Rad2 (second RadUpload), the RadUpload.UploadedFiles for the first RadUpload is there (count = 1). Instead of the file being uploaded by Rad2, it is detected as if it is uploaded from Rad1, so my validation failed.

Does someone encounter this problem before? This is a very weird thing and I've spent almost 1 and a half day fixing this without knowing what happened to the control