I would recommmend going back to DX7 right now as well. I'm not certain if DX8 is in final stages yet outside of WINME, but I had nothing but problems with .dll 's and the like when I had it installed.
I recommend gettting DXunistaller from Download.com. Very safe and I've used it numerous times. ABout 10 now.
The Jolly Wizened Oaf!