carefully clean the dock connector of your iPhone with a dry SOFT toothbrush and a little compressed air. You may have some debris shorting out some of the pins.

If this doesn't help, its possible the device you connected it to has caused internal damage (some devices "Made for iPod" are not "Made for iPhone" and can damage newer devices).

This reply may be redundant, but yes everyone is right on the money with water damage and dock connector issues causing this problem. Definitely check your dock connector for pocket lint compacted down in it. I have seen iPhones with so much fuzz jammed into the dock port that the power charger won't even lock into place properly! If you get a little moisture on this "lint jam" it can short your connector.

Unfortunately, it is nearly impossible to replace a dock connector on a 2G because it is so intertwined with the midframe and also requires removal of top glass and LCD because the flex assembly is also part of the home button. (Man I'm glad Apple changed this design with the 3G!) You'll likely damage more stuff trying to replace a dock connector on a 2G than it's worth.

I suggest buying the entire 2G top glass/midframe assembly (provided of course you don't have water damage evident on the logic board) I've used this unit from Hong Kong for $98.00US (free shipping) a few times(Cosmax I believe is the company name and expect 14 days for delivery). It makes easy work of just about any 2G repair since all you're going to use from the broken phone is the logic board, camera, aluminum back housing with head phone/button flex assembly and the black plastic outer antenna cover.

Sometimes these symptoms can occur from water damage to the dock connector area and/or corrosion in and around the dock connector from humidity/moisture. You can try to clean the dock connector with some alcohol on a cotton tip but this does not always work, your best option would be to examine the extent of internal corrosion and replace your dock connector.

OPK, You ROCK! Haven't fixed the dock connector yet, but my new symptom is the camera view on the screen is in vibrant reds, with a little blue in the black areas. Does this suggest the corrosion is progressing?

rhutchis I suggest you crack it open and take a look, the corrosion should be relatively obvious. I am not 100% on your camera issue, it could be related but I am not sure.