Create / update Activity : TokenInput widget is completely broken (incorrect contacts set for target and assignee)

Setting (and removing) of target and assignee contacts from Activity insert and update is not working at all.

Examples:

• on New Activity, I selected a contact for the WITH (cid=23 in several tests) - BUT the activity was saved with a different contact in the target_contact column (cid=2). I tried this from the Activity tab for cid 23 AND via standalone (New Activity from top nav menu). Same erroroneous results
• on Editing an activity, I removed the current WITH contact (by clicking the X) - and selected a different contact (cid=23 in this case). After saving, my Activity record had TWO target contact entries - the one I had deleted in the With contact jQuery widget field AND another one (but not the one I had selected in the widget). In another test, I removed target and added a new one, and ended up with NO target contact.

I tried emptying my browser cache in case there were some updates in the jQuery widget code that I wasn't picking up - but that didn't help.