I'm on iPhone 2G with the same problem:
no thing connected in dock or headphone jack but the "this device is blahblah" message comes up draining the battery life etc.
I used the IAPD fix since 1.1.4 up until 2.2.1
Was waiting and refreshing this page for a couple of days until I thought SOMEONE'S got to try it - and I went ahead.
I can confirm that the IAPD file is still there (the previous poster got confused as the folder name is called IAP.framework)
I went through a few "tweaked" IAPD files and managed to find one that works like it did on 2.2.1
I'll upload it soon.
EDIT:
Download Link
Methods are identical to 2.2.1, I'll briefly outline them again though
Before carrying out these instructions, when updating to 3.0, you should back up your phone on iTunes and you must have iTunes 8.2 installed.
Jailbreaking for 3.0 is only possible with PwnageTool at the moment (QuickPwn isn't out yet so beware Windows users)
1. Download the iapd file above.
2. Enable SSH on your iPhone (I think it needs to be jailbroken. I used OpenSSH on Cydia)
3. Download WinSCP for Windows users, or Cyberduck for Mac users. Any SSH client would do though.
4. SSH through your iPhone into: root/System/Library/PrivateFrameworks/IAP.framework/Support
there should be a file in there called iapd (no extentions)
5. rename this to iapd.bak (backing up to be safe)
6. upload your recently downloaded patched iapd file on to this folder
7. IMPORTANT: set permissions to 0755 if not done so already, failing to follow this step could lead to your iPhone bricking and in need of a restore
8. Reboot and pray
This worked for me, but may be different for other iPhones. Worst case scenario is that you'll need to restore your phone and downgrade it to 2.2.1 and apply the previous iapd file that worked for you prior to the 3.0 update.
Feedback on this method is appreciated!