Q: My Mac Doesn't Show to Others on AirDrop

I have a MacBook Pro 15" Retina Display running the latest Mac OS X 10.8.3 with all the updates. My Mac is obviously supported by AirDrop as it is a current model. When I 1st got it, I used AirDrop all the time to transfer files back and forth with nearby colleagues. Then one day I went to use it as I always did and noticed that my Mac no longer showed up to others when we both went to AirDrop. I could see their Macs, but they couldn't see mine. I verified this later with my own MacBook Air 13" (current model) I could see the MacBook Air on the MacBook Pro, but not the other way around. The only way my MBP shows up on thei other computer is if I initiate a transfer to theirs it shows up long enough for them to accept the transfer and do the trasnfer. Once the transfer is complete my MBP disappears from there's again even though AirDrop is open on both Macs.

Here's what I've tried based on all the tips I could find on my searches.

Yes my MBP is supported by AirDrop (it used to work just fine)

Yes both Macs have Finder windows open with AirDrop active (it used to work just fine and I'm aware of how to use it)

No, the Firewall is NOT enabled on my MBP (never has been).

Yes, WiFi is on

Removed my Apple ID from Users and Groups and put it back in again.

Repiard permissions and the disk.

I have an external drive that I sometimes boot from for beta testing software. When I boot from that drive AirDrop works! So this leads me to believe that it's something to do with my internal drive's OS.

One tip I saw was to boot in Safe Mode (shift key down) and Repair Permissions. This is where I ran into a new problem. My MBP would hang during the Safe Boot. The progress bar would bet about 1/3rd the way through before just hanging. I let it go for hours and it never booted. After doing a little research I decided ti was time to backup my drive, boot from a clone backup, REFORMAT the internal drive, install a fresh copy of 10.8.3 and have it put the data, apps back on from the backup. After this process was done I tried AirDrop and IT WORKED! Problem solved! Or at least I thought. I closed the MBP after putting it to sleep and moved it back to my office. Woke it up and just for kicks I tried it one more time and to my dismay I could see the MBA, but the MBA couldn't see the MBP anymore!!! I didn't change any settings. It worked once, but now won't work again.

I rebooted and it worked! Woohoo or at least I thought. A few minutes after that post reboot success I tried it again and it didn't work. So it seems that it works soon after a restart and then it dies. I tested this theory with another Restart and sure enough the MBP showed up on the MBA (after about 20 seconds, whle the MBA shows up on the MBP immediately every time). I close the window on both Macs and try it again and the problem is back. I only get one use of AirDrop after a reboot from the MBP.

I'm at a loss as to what to try next. There has to be some preference somewhere that's keeping it from showing my MBP on other Macs.