I ran into an interesting issue with a site that my company hosts this week, and I thought I'd share the problem description and solution. A number of files and images started to fail to return, saying that either they could not be found or that the user was not allowed to view the file. Those ColdFusion pages that did return would say that they couldn't find the specified files either.
In the end the only thing that fixed it was a service restart. We tried a blanket update of permissions to make sure nothing was amiss, but that didn't work either.
I'm still confused as to why a ColdFusion service restart would clear up the issues with images though. My theory is that permissions had been messed up, but that CF was caching the permissions until the service was restarted. I ran into a similar situation trying to work with SQL Server, where I was forced to restart the service to get CF to acknowledge changes in user permissions. If the permissions were messed up and CF cached them, maybe we didn't check the gif before restarting the service to get things back.