All of my AE file are corrupted - even my auto saves

What would cause this???? 

Every single .aep file gives me the same error. That its unable to import the tile 'name' as project (bad format or not readable) its like 40+ files that are corrupted? I moved these files onto dropbox and then back out? Would that cause this? I tried opening them in both the current verison of AE and older versions. No luck. 

I don't have a lot of hope this can be resolved, but how can I avoid this in the future?