All the solutions given above do not work for my HTC (desire S). I accepted the fact that I've to switch off the speaker every time when I call or get called.
After I accepted this annoying bug the next problem occured. My navigation (app) activates itself all the time (not google maps but the app with the blue arrow).
I tought something was wrong with my settings but it isn't. Two roommates have the same phone but they don't have any problems with it.
It starts to get really annoying because it takes the app about 5 seconds to start and then i have to activate GPS before i can close the app (so in total it takes me 10 seconds to just activate my screen and see what time it is or what message I received).
I tried everything: take the battery out, do a total reset to factory settings, nothing works.
I also tried to delete the App, but thats not possible because its integrated in the phone. You can almost delete every app but you cant delete the 'Navigation' app.
Does anybody have any hints or suggestions to delete the program or to find a solution? I'll be very thankfull.
I don't care to delete the app because I can always still use google maps for navigation.
(my englisch isn't very good, so please ignore the little translation mistakes i made)