Problem fixed with Itunes "restore" (while iPhone plugged into it). Note that in my above post, I tried the hard reset of the iPhone by holding the 2 buttons down at the same time. This did not help.
I think the source of the problem was with the list of "syncing" music. To see this list, open iTunes, plug in your phone, and in left hand column in iTunes, click on the arrow beside your phone to show contents of phone. Click on music. Songs for me fell into 3 categories:
- exclamation mark beside them (as if iTunes could not find the music file)
- check mark beside them (synced, all ok)
- greyed out, "sync" symbol present, and "kind" of music absent (waiting to be synced)
iTunes would sync some songs, but not all songs. I could get about 60% of all songs onto my phone.
To recap: my initial problem was that some songs on my iPhone would not play and some songs would skip over to the next song, and if I used FF or to go to next song, could completely hang up all playback of music on iPhone.
The "restore" appeared to refresh the list of "syncing" music. Since all original files on my computer were not corrupt, I did not have to convert or delete any of my music files.
I don't know why this occurred. It is possible it occured when I initially bought and synced my new iPhone 4s with iCloud. It is also possible that it is a wi-fi sync error. I am very interested to learn how or why it happened.
Hope this helps someone.🙂
Jason
iPhone 4s with iOS 5.0.1 and using iMac for iTunes