I think it may be confict with DEP. You can disable DEP in boot.ini. Change /NoExecute to /Execute.

In DS3.2. There is not usermodebreakpoint. Bpx now have parameter .t|.p to set breakpoint on thread or process. So it need not usermodebreakpoint now. If you set breakpoint with no param, it act as 2.7 before, break on every process.