So I bought and installed the aux input in my 05 cabrio, all was well. It was working great.
While driving around, it stopped working one day. I dropped the knee panel, pushed on the plug... and it started working again. Thought nothing of it, then it happened again. And some more times. Then I started hearing static, and would get a loud interference buzz whenever I plugged in my iPhone. And it stopped completely. And now, I hit mode and get nothing as if it's not plugged in.
I pulled out the plug completely, checked every connection, everything looks seated and strong. Pushed it back, heard the click, and still I get nothing. Is there a fuse I blew maybe? Could it be the actual plug? Or is it possible to break something in the back of the stereo? Any ideas?

Most likely a ground loop, this worked for me (my aux would do the same thing):
PAC SNI-1/3.5 Noise Filter

I've read that that could be it, but I can't get it to work again to be able to see if that'll help? I think I might need to try tearing up the wire and resplicing. Thanks for the reply.

Before you splice the wire, try connecting your iphone (or another device) while it's running on it's battery (ie, not plugged into a power adapter)

This will let you know if its a ground loop or not.

Nothing at all. It won't switch to Aux anymore.

Thought I'd post an update since this issue resolved itself kinda...

Somehow the fuse that covers the cigarette lighter and some dome lights went out. The aux input started working again, and it hasn't gone out since. Probably because I haven't replaced the fuse and thus haven't created a ground loop between the charger and the stereo. So for future reference take out the fuse for a little bit, if it stops working.

I am having the same issue. I installed the kit and it worked for about a minute. I told the company I ordered it from so they sent me a new kit. I installed it and it worked, for about a half hour. Then I started over and it worked fine as long as I didn't screw the radio back into place. Then it stopped again and now it won't even recognize AUX as a mode. Mini wants $600 to install the kit and I really just refuse to pay that, but I want this done. Does anyone know what it could be? I will try the fuse thing, but I have never gotten the kit to work continuously so I don't know that the fuse is the problem. Thanks for any help you can provide.

Are you plugging your device into the charger at the same time? You can charge it or you can use it as aux input, but you can't do both at the same without a ground loop isolator thingie. I thought the fuse made a difference, but it's the whole resetting thingie that does it.... Try this, unplug your battery for an hour or so. Your aux input should work again. Disconnect your cigarette light charger to avoid temptation and you should be fine. If someone borrows my car, they'll plug both in and my aux input won't work in. Hide it in your glovebox or something.

I have never had my phone (which I use to play music) charging while I had it plugged into the AUX. I have had the charger just plugged in not charging anything though...would that still do it?