Just a few thoughts, direct from the website:
1) Firmware with/without the Game Controller device.
Starting with version 34 there are separate firmware versions which have the game controller device present/not present.
Versions without game controller (ie with keyboard and mouse support) have the first version digit as "4" eg 1.44.
Versions with game controller (ie with gamepad button, keyboard and mouse support) have the first version digit as "3" eg 1.34.
When changing versions it is necessary after the firmware change to locate the "composite device" under the USB Controllers entry in Device Manager and "Uninstall" this so that Windows can re-detect the new version correctly.
Have you tried this ^^ anyway? Even if you didn't change the firmware...It can't hurt.
2) It could also be something in your wiring is amiss or sticking. Try disconnecting everything & hooking them up 1 at a time until you find a problem.
3) Also, don't forget about the IPAC Shift key(usually P1 Start & you said that was sort of repeating like it's stuck on when you hit another key). If it's sticking on or something it'll mess things up for the IPAC.
Those are a couple of easy things to check before you contact Andy. Let us know, maybe someone else has a better idea to try.
Pessimist: Oh, this can't get any worse!
Optimist: Yes, it can!