There is no build-in way to disable interrupts while stepping.
On PSoC3, the user can do it manually by setting the EA bit within the IE register to 0 before the step and 1 after the step. This is one of the standard 8051 registers that is listed in the disassembly window.
Having a 100ms interrupt is a hard real-time requirement, single step is a different domain, the non real-time domain. Unfortunately these two domains do not go well with each other.
I hope this helps, Robert
This isn't any more great news, but my work around for this has been to keep moving breakpoints around and not use the single-step feature...
One thing that I have tried in certain cases is to comment out the global interrupt enable call, then I can step through some code. Of course, in most cases this won't help much...