F% all the dumb crap. install tversity on your computer and problems go away. (www.tversity.com)
I stream high def mkv files (11 gig rips of blu-ray) with tversity. couple of tweaks to get it setup right, but they are simple option tweaks in the settings. the main tweak is to set your video size to 1920 by 1080 so you can stream 1080p I stream divx, avi, mp4, mov, wmv hd, mkv with no probs. the only gay thing is that when you want to stream, you gotta start your tversity and click on start sharing. with wmp11 you dont have to, but you also dont get all the formats, and you have system resource issues with it once in awhile. you prolly can leave tversity going 100% of the time if you wanted, its sorta like vlc player, uses very lil resources. make sure you have a bunch of codecs installed, since tversity will use the codecs at will and transcode it to a useable format for the 360. also, tversity is supposed to allow web streams to stream on your 360 as well, but i havent tried to get that going yet.
another note, my setup here.....
behind the modem, i have a linksys wired 5 port router, and never could get them to connect thru the router. so i installed a netgear 4 port hub after the router. there is another 4 port hub upstairs for the pc and 2 360's up there. before tversity, they couldnt see my pc. after tversity, every 360 can see every pc in the house (3 360's and 3 pc's). I am setting up the gf's old pc now to mainly be a storage unit for streaming duty, and put files on there i will know i will keep long term.
tversity works for ps3 also...
