SSRS says people that have access to a report don't have sufficient permissions to view the report

Question

I have a report that I want to grant people access to. There are three people I want to be able to see this report: myself and two co-workers. The security has been set up like so:

BUILTIN\Administrators Content Manager 
<domain>\User 1 Browser 
<domain>\User 2 Browser, Content Manager, My Reports, Publisher, Report Builder 
<domain>\Me     Browser, Content Manager, My Reports, Publisher, Report Builder 

Myself and user 2 have the exact same roles. But I am the only one that can see the reports. Everyone else gets this:

An error has occurred during report processing. (rsProcessingAborted)
The permissions granted to user '<domain>\User 1' are insufficient for performing this operation. (rsAccessDenied)

I don't understand how the other users can't access this report. Has anyone encountered this type of thing before?

Answer 1

It appears that the problem was the reports in question used shared datasets, so I had to grant permission to the datasets and datasources folders in Report Manager so the reports could then be viewed.