So I’ve been trying for hours now to get just about ANY version of Mono develop to actually run on a Mac (seriously Unity needs to get their crap together about this); I’ve since come to the conclusion that I am unable to do so with my own knowledge and therefore I’ll start back with the newest version of Monodevelop and see if the community can’t help me out 
So I’ve put the crashlog on pastebin; basically it seems to be saying Monodevelop cannot read the file /Library/Caches/MonoDevelop-Unity-4.0/addin-db-001/addin-data/1/MonoDevelop.VersionControl,4.0.1.maddin —>. I’ve checked and the file is indeed there, anyone have any ideas why it is throwing this error?
Crashlog:
I just had the same problem and I managed to solve it. I had installed Unity to an external hard drive and Unity itself was working fine. Monodevelop, however, was not.
I moved MonoDevelop.app to the standard Applications folder on the main hard drive and now it seems to be working fine. I also deleted ~/Librar/Cache/MonoDevelop-Unity-4.0/ in the process but I don’t think that mattered.
/Daniel
I have had he same issue as I installed an SSD on my Mac as a boot disk. (Mac OS X 10.10.2)
Unlike any adventurous person, I decided to keep the Mac HD, but used CCC to copy everything to the SSD. Did the re-targeting of the boot disk and ended up w/ the same issue above. Also to mention, I did not want any more applications to go to the HD, only to the SSD. Needless to say so have been Unity3D apps in the install process to the SSD.
The installer let’s one chose to install to a target, but funny enough, the “Documentation.html” still ends up in the HD/Application folder.
So after reading this post, I did several tries and failures.
The answer is for the Boot HD vs. external SSD in my case:
Instal Unity3D on the drive you desire, pick the one you like!
Let it install.
Drag over the MonoDevelop to the HD-Boot-Disk.
It will show as “Not-Executable” the “forbidden” icon. Ignore that
Make an “Alias” by right clicking the MonoDevelop icon!
And drag it back to your SSD folder.
All happiness should be restored when working w/ U3D from the SSD.