Having to keep reloading files!!

Hey to whoever can who answer this issue,

I am currently working in AE CS5 doing a lot of basic motion graphic projects using illustrator files and such. I have noticed with a lot of my projects lately that I have to reload some files when I reopen the project. When I open the project, some of the layers of a file will be there and some will be not there! Once I right click and hit reload, it comes back! So I'm not really losing any of my stuff, its just an inconvenience for me as everyday I come back to work on the project, I have to reload a butt load of files/layers!

Anyone have a clue to what is the cause and how to resolve this issue?! It's gotten to the point where I just leave AE open over night and don't even close it!

Thanks,

Blake

This has seemed to be only with illustrator files as that is what I am mostly working with... I have worked with some photoshop files and jpegs in the past but cannot recall having the same issue!! Do you have an answer!!