4.0-5834 isn't the build that added the GC adapter code. What it did was to fix problems with using more than one GC adapter on one computer. If you use a build that is slightly older than that, GC adapters should still work fine as long as you only are using one.
As for the actual issue with 4.0-5834... Hmm, I haven't heard of any problems with that version before, but it's entirely possible that there's some USB crap that's preventing it from working on your computer. It's happened before, with the version that added GC adapter support. NKF98's suggestion is worth a try (but remember to backup the Dolphin Emulator folder if you want to keep any save files!) but it may or may not work.
As for the actual issue with 4.0-5834... Hmm, I haven't heard of any problems with that version before, but it's entirely possible that there's some USB crap that's preventing it from working on your computer. It's happened before, with the version that added GC adapter support. NKF98's suggestion is worth a try (but remember to backup the Dolphin Emulator folder if you want to keep any save files!) but it may or may not work.