berntd,
just a thought...
Recently I had issues with BIAB playing and failed renderings. I tried switching drivers, etc. Nothing helped. I did factory settings reset and that solved it.

If it was not suggested earlier, maybe try it? It takes less than a minute and it does not involve reinstalling software. If you want to give it a shot:
Options->Return to factory settings.

One other thing you can try is loading Windows with minimal set of driver/program load and see if issue persists. Also upping the buffer on Asio4All...

Good luck.