NOTE: If you use ansicon make sure it is not loaded
Download the Oniguruma library.
I have had good luck with 5.9.1 and 5.9.2.
I used C:\Users\gthiesfeld\Work\repo\onig-5.9.2.
C:\>\Ruby\DevKit\devkitvars.bat
Adding the DevKit to PATH...
C:\Users\gthiesfeld\Work\repo\onig-5.9.2>sh configure
... output snipped ...
C:\Users\gthiesfeld\Work\repo\onig-5.9.2>make
... output snipped ...
set CPATH=C:\Users\gthiesfeld\Work\repo\onig-5.9.2
set LIBRARY_PATH=C:\Users\gthiesfeld\Work\repo\onig-5.9.2\.libs
C:\>gem in oniguruma
Building native extensions. This could take a while...
Successfully installed oniguruma-1.1.0
1 gem installed
Installing ri documentation for oniguruma-1.1.0...
No definition for oregexp_initialize
Installing RDoc documentation for oniguruma-1.1.0...
No definition for oregexp_initialize
That's it. The errors at the end are due to rdoc and ri not being able to parse the source. If you see these, don't be alarmed.
Legend, lifesaver.