I am a beta tester for SwitchRes and version 2.0 is about to be released. I'm runing it on my 8.6 system and it runs beautifully.
The incompatibility between 8.6 and SwitchRes 1.x is a known issue and will be fixed when version 2 comes out. Just to let you know, version 2 includes tons of great new features as well.