Ok so you already updated the service books (reg now)
This actually happened to me before what I had to do was start up DM, then disconnect my PC from the net and then connect the phone to the PC, then click on "application loader" (you may get a prompt to update the core applications and you want to accept that and let it run). This should reinstall the app center. Also in app loader it should let you check and uncheck what items you want to install.
Edit: also verify that it app center is gone because if you are coming from .75 or earlier the app center symbol has since changed (in .83 and .85)
got it back yeah baby now can someone tell me how to get the .85 update on my phone. i downloaded it but have the same problem dave had. Dave if you could help thatd be awesome man.