Have you tried clearing the program cache/renaming the personal Config folder as of yet? This will catch all kinds of weird "just started happening" issues...
Deleting a corrupted cache file
If that does nothing, restoring preferences to factory default can clear up issues with extension conflicts that cause weird behaviors...
http://helpx.adobe.com/dreamweaver/kb/restore-preferences-dreamweaver-cs4-cs5.html
You can have both programs installed simultaneously, as I'm sure you've noticed, but if you still have issues with DWCS6 after doing the above, a full clean reinstall using the Adobe Cleaner Tool will generally fix it...
Use the CC Cleaner Tool to solve installation problems | CC, CS3-CS6
If none of the above do anything, try creating a new admin level user account and see if the program functions. I've seen it a few times here in the forum with Macs where the new user account brings the program back from unstable/unusable.