Asp.net 4 FileUpload gets "Permission Denied" when Uploading file

Hello,

There's 2 apps that upload files.  Both have been running fine.  Files were able to be uploaded.  I uploaded a file through it 3 days ago and it worked.  This morning it comes up with an error: "Access to the path 'D:\.....' is denied."

It's happening write at this code line
      FileUpload1.SaveAs(thisSaveServer + savePath)
I looked at the code for thisSaveServer and savePath and it looks good - hasn't changed

Here's the weird thing.  There's 1 IIS server and 4 webs on it.  2 Webs for testing (A & B)  2 webs for production (C & D)
In each case Web B uploads to Web A and Web D uploads to Web C.  A Virtual Directory is used in each case.
Production (Web D->C) works great
Testing Web(B->A) gives me an error.

I copied the .aspx file from Production to Testing and got the same error.  So it's not the code.

I look at the permissions and they are identical.   IIS_MACHINENAME  has full control
For the application pools identity they are using ApplicationPoolIdentity

Here's something new: I was able to upload 1 file and not the other.  These are all pdfs.  When I opened the pdf files on the server -  go to properties -> Details -> The one that wouldn't upload says Owner = Administrators.  The one that did upload says Owner = App Pool Identity name.

When I open the pdfs on my desktop that were uploaded they both have me as the owner.

Any ideas on where I could investigate and find what's happening?  Talked to the server guys and they said they didn't change anything.

Jess