That is seriously annoying isn't it. My workaround, is

1. Edit the caption style to add a tab to representing the distance of approximately 2 or 3 spaces after the :
2. Edit the Table of Figures style to add a hanging indent and a right indent
3. At caption insertion time insert the tab

The down side is I don't get a uniform space in the captions between the : and the text, and if there are more than 100 captions the gap gets too wide and forces direct tab over the still. Still, I prefer that rather than having to reformat the TOF every time updated.

If anyone has a more foolproof workaround, I would be very interested to hear it.

Hope this helps.