The project was not built due to "Could not delete 'project/bin/classes/com',"

I've seen this error before and I've solved it before by just cleaning a project but this time it just doesn't work. This error sometimes appears when I import a certain project from existing code. Things I've tried so far: Clean the project (this fixes it just for long enough so I can compile it but then the error reappears, it gets annoying to clean the project every time when I want to compile it) Deleted bin folder manually and then cleaned the project (same effect as "clean" option, it fixed the problem for a minute) I've done a lot of research on this and everyone says that cleaning the project should fix it but it doesn't. EDIT: Some additional details: I'm using the latest version of eclipse My workspace is in a Dropbox synced folder because I'm sharing it between two computers (maybe the problem lies there?) When I click on the console tab, there's one more error saying "unable to write jarlist cache file C:/users/user/dropbox/android development/workspace/project/bin/jarlist.cache"