Cygwin error: “-bash: fork: retry: Resource temporarily unavailable”

(assuming Cygwin is installed at C:\Cygwin):

1. Open Task Manager and close any processes that look to be Cygwin related.
2. Open C:\Cygwin\bin in Windows Explorer
3. Verify that dash.exe, ash.exe, rebase.exe, and rebaseall exist in this folder
   • If any of them are missing, re-run Cygwin setup and select the dash, ash, and rebase packages
4. right-click your C:\Cygwin folder, uncheck Read-only (if its checked), and press OK.
   • When an error about not being able to switch some files comes up, select “Ignore All”. Wait for this process to complete.
5. Browse to C:\Cygwin\bin in Windows Explorer
6. Right click dash.exe and click “Run as Administrator”. A command Prompt should appear with nothing but a $
7. Type /usr/bin/rebaseall -v, hit enter, and wait for the process to complete.
   • If you get errors about Cygwin processes running, try Step 1 again. If that still doesn’t work, Restart your computer into safe mode and try these steps again.
   • A commenter noted that, depending on your settings, you may have to type cd /usr/bin && ./rebaseall -v instead.
8. Try opening Cygwin again.

This process worked for me. I hope it works for you guys too.

Source: http://cygwin.wikia.com/wiki/Rebaseall