Sync for IPod Touch quit working and I get error messages "a session could not be started" and "a connection could not be established" although the IPod appears in ITunes.

This is a new problem for an IPod Touch I have had for a year. The IPod is hooked up by cable and appears in ITunes. I can examine all the content on the IPOD and I can click "sync". It goes through to Step 7 and then the error messages occur. First "a session could not be started with the IPod" and when that dialogue box is closed, the message "a connection could not be established to the IPod."