Thanks everyone for the help... After checking and trying several other options, the problem seems to only happen when ever i load props with missing links... This message appears when a prop with missing links is loaded:

"Failed record undo/redo step. Undo manager will restart."

Now, when that project is saved, it cannot be reopened. This is happening from content I transfered from another computer or installation. I've removed those props and made a fresh install of the content pack and the problem has not come back yet.

Thanks again