Backup-SPSite gives an error: "Operation is not valid due to the current state of the object"

I got a backup of a Sharepoint 2010 site that I created from our client's production server so that I can make some new changes to it on my staging server.

I can restore the site collection from the backup without a problem but when I try to create a backup of the same site on my staging server, I always get the error "Operation is not valid due to the current state of the object".

Before the error is given however, a small part of the backup file is created. If I try to run the Backup-SPSite again, it always f开发者_高级运维ails at the same point and the corrupt backup files are always the same size.

Going through the logs it looks like the problem might be related to user permissions. I wonder if it's possible that the user permissions, user data, etc that came over from the client's production server are somehow screwing the backup process now because the same data cannot be found on my staging server.

The same error is mentioned here http://technet.microsoft.com/en-us/library/ee748617.aspx but UseSqlSnapshot parameter doesn't work anyway in my case.

I've been hitting my head against the wall with this problem and would appreciate if anyone has any advice on what might help! :)

The setup:

Windows Server 2008 R2

Sharepoint 2010 Server (no SP1 because it hasn't been installed on the client's production server)

Microsoft SQL Server Express Edition

Cheers!

The backup process started working after I checked in a file that had been checked out by a user on my client's production server.

I found out what file that was by opening the corrupted backup file and looking at the title of the last entry.