Dropbox icon unresponsive and will not sync.

So the first time I downloaded dropbox, when I first turned on my MacBook Pro OS X, it worked perfectly. It downloaded, it synced, it worked. Then when I turned my computer on again, the icon in the toolbar had a spinning rainbow circley thing (not sure what you call that - it's like the windows hourglass thing) over the icon. None of the other icons in the toolbar seemed to be affected, just the dropbox icon. I couldn't click it, I couldn't sync it to any changes I made to my online dropbox account, and regardless of how much I searched for an answer to this problem online, nothing seemed to work. So far, of the many things I've tried, this is what I have done to attempt to fix this problem, all of which have been failures with the exact same result each time:

• I've completely deleted all dropbox associated apps and folders and anything with the name dropbox in it, then redownloaded the .dmg file. (Failed)
• I've tried only deleting the .cache files. (Failed)
• I've tried deleting my antivirus, as one solution that seemed to work for someone else stated that it may interfere with the program. (Failed)
• I've tried reducing the amount I wish to sync at one time to below 1gb. (Failed)
• I've tried using the Terminal app to delete it and then redownload it. (Failed)
• I've tried to find an earlier form of the downloadable .dmg file to see if recent updates to dropbox may have interfered with the OS X system. (Failed)

I am unsure about what else I could possibly do to fix this seemingly impossible to fix problem. It is not a matter of just giving up on my end since I use dropbox for a majority of important files that are necessary to both school and home projects. I require dropbox to be accessible on my home computer (my MacBook Pro OS X) and so far, that has not been possible. Please help me try and fix this problem, and I apologize in advance if I seem stubborn on this point. I have spent an annoyingly long amount of time trying and failing to fix this problem and have become frustrated as time went on. Please bare with me and help me find a solution. Thank you for your time and effort regardless of the end result.