This is a common problem on 99- Volvos. Its a matter of time before someone ends up being killed. Mine failed on my 99T5 on the motorway in the UK and like yours the car more or less coasted to a stop. 10 minutes on hte hard shoulder and it restarted and went for about 20 miles before doing it again... and again... and again...
A full clean of the TCM sorted the problem for the next 15k miles but like a bad penny back it came. This time it came back while on a back road and passing a truck - fortunately there was nothing coming! I then finally had the TCM replaced (tried to clean it again (see my details on http://www.rally-photos.co.uk/volvo/tcm if you are brave!) but it wasn't having it). When I spoke to the parts guy he said they have lots of these fail (and in particular the police seem to burn them out with monotonous regularity - this is the UK and they use V70T5s for pursuit!). They even keep 3 in stock at the Sheffield dealer! So this is obviously not an unknown issue to Volvo...
Incidentally, someone from Volvo (192.138.116.163 - httppxgot2.it.volvo.com) has also looked at my website to see how to clean the TCM! Since this page on my website is not searchable by any search engine and has no external links that can only mean Volvo personnel monitor this forum... So come on Volvo. This is a serious safety issue! Come clean and do something about it!