Procedure call does nothing?

I am calling a procedure (A) from mainproc (key and stylus handling routine). In my code this procedure (A) calls another procedure (B). When I run the code it is evident that procedure B is not being executed. I deugged this in PIDE and found that the call was just being ignored. I 'stepped into' the call but nothing happened - it just went onto the next line of code.
Both procedures were working before when they were called from a button press. They are now called from a stylus tap. The parameters are correct. Any ideas?
Both procedures were working before when they were called from a button press. They are now called from a stylus tap. The parameters are correct. Any ideas?