The problem with using the islave model as a player model is that it lacks proper animations for HL multiplay. Use HLMV (link on links page) to see this model out of the game and to look at it's animation names; compare it to that of the player models and you'll find they're different.
You need to create new animations for DM play if you want it to work properly, or decompile the model, and hack the qc to rename the animation references (smds) to DM ones. There's a tutorial on modelling and simple qc hacking on this very site.
For more advanced modelling tutorials and help, the good folks at the Half-Life Improvement Team may be able to help you out. (Be sure to register for the forums and check out all the stickies in the 'Help Desk' forum for some good tips and tutorials.)
http://hl-improvement.com