I just googled and found this page. It's been a while....
Just snaged the dosboxcvs-060518 precompiled zip and loaded it up. lo and behold runing in direct3d mode I get "SDL:D3D:Cannot lock texture!" infinitly.
I too am running win2k though I do have a dx 90b sdk from back when I was fiddling with directx (not installed right now)... Figures MS is trying to push win2k out before it's support cycle is up they aren't supposed to stop supporting something until the 2nd generation (ie vista) is actualy out... Officialy anyway.
<thought strikes while typing>
I seem to remember fixing a bit of a problem with another recently released game by grabbing a file that was supposed to come with some distributions of directx that somehow wasn't always included. Also somehow dxdiag misses that you are missing a critical file for some newer games...
Now if I can just remember what game it was <grumble>... It's possible we are all missing this file.