C++ Program Executables not Running from Scheduled Tasks

I have written a number of programs in C++ which take data from large text files and condense it into smaller files that can be uploaded to our website and used by local apps. These had been scheduled to run daily on a Windows 2003 server, and worked just fine as such. However, since we migrated to a Win 2008 Server, these programs refuse to run in task scheduler. They work if I execute them through win explorer or command line, but they either hang or return a 0x3 error from scheduled tasks. At first, I thought it had to do with the fact that the programs copy files from remote locations, but after I made everything local (the programs now only read & create files in their own directory), it still doesn't work.

I am running the tasks as an administrator, with highest privileges.

No idea what to do now.