Problem with Inventor's Projects

[jdiwnab]

I have a project for the our robot and put everything in there. Eventually, the one folder got confusing and so I put related parts in their own folder in the project folder. eg: the chassis frame parts in the folder called "chassis" is the folder "project". I put arm stuff in "arm" and I put the folder of the Virtural Kit of Parts in the project folder too. Put when I opened the main assembly that was directly in the project folder, some parts couldn't be found by Inventor. It put me in the right folder, but wouldn't select the part. I thought I had fixed it, but it happened every time I re-opened the main assembly. Inventor tells me that the selected item isn't in the current project, but it is in the right folder.

What's wrong here? This isn't a big problem, but is increadably anoying to have to reselect the parts everytime.