For this sort of thing, we've been using Package Configurations stored in an XML file. This allows us to change properties (like file paths) without rebuilding the package. But that's a completely different topic from Checkpoints...

However, one error I encountered along these lines was when I changed a property in the package (in BIDS), and saved it, but either (a) failed to build it, or (b) built it, not realizing that the build-path was different than expected.

This is a real basic error, true, but I've done it, so I mention it here. Just make sure that the changes you make in BIDS are built into the package (*.dtsx) you're actually executing. And (as Aaron mentioned) that the pathname is accurate--a network server pathname would be better than a locally-relevant pathname (i.e., \\Server01\SSIS\path vs. D:\SSIS\path).

k