It seems unlikely the OP is ever going to return, so I’ll address two specific cases that could have caused this:
When you have to enter credentials to access the network resource or if you are operating on a mapped drive, elevating a process may fail because of UAC.
This is because with UAC you are actually logged in with two sessions, one with administrative access and one without. These sessions are mostly separate, they don’t share mapped drives or network login tokens.
Your non-admin session has its mapped drives and any network login tokens. After confirming the UAC dialog, Windows tries to load the program in the admin session. It doesn’t have any network login tokens nor the mapped drives. As such, it will fail with either “file not found” or “access denied”.
Microsoft describes this behavior in greater detail in this article on TechNet.
Luckily, there is a workaround, enabling “Linked Connections” (described in the article mentioned above). The following
.reg file will accomplish this:
Windows Registry Editor Version 5.00