I regrettably had to return my Droid today to Verizon for this very problem. The problem, is that anytime I use the headphone jack to listen to tunes or podcasts in the car and then remove the chord from the jack both the phone speaker (the actual speaker for the phone that is at the top of the touchscreen) and the speaker phone do not work. The only way to get them to work again is to reboot the phone. This is the second phone I have had with this problem, and Verizon seemed unwilling or unable to let me exchange it for a third phone.
Because I bought the Droid to replace my old smart phone and my Ipod, not being able to easily switch between music and phone calls was a dealbreaker for me. I was up against the 30 day return window with Verizon, so I had to decide whether I wanted to wait on a software upgrade to fix the problem. A software upgrade that may never come.
I ABSOLUTELY LOVED the Droid otherwise. I guess I will just have to wait on another Android phone to come out that I can use with Verizon (maybe an unlocked Nexus One) or just get a iPhone in a couple of months when my Verizon contract runs out. I have searched the forum and have seen a couple of threads that touch on this issue, but they seem to all meander into posts about a static problem in the headphone jack which I did not have. Is this a widespread problem? I have to believe it is since both my phones were essentially doing the same thing.
The worst part is that now I have to reactivate my WinMo smartphone. It's like going from HDTV to a 12" black and white TV
I have the same issue and my fix so far has been to simply make a call to my voicemail immediately after disconnecting the headphones. Works like a charm.