Sometimes, when I load uV2 and start the debugger and press F5 (run) I get this error message: MONITOR ERROR 6: CANNOT WRITE BREAKPOINT When this happens, the program is not running, but if I press F5 again, all is well. I don't disable the global interrupt enable (IEN) anywhere in my app. I can set breakpoints anywhere in my app (after main() is called from the startup ASM code) and the debugger seems to work just fine. Every time I exit and re-enter the debugger (usually with a re-build in between) and restart debugging, I no longer get the error message. Anyone know why I might be getting the error message just once, not always, but when I get it, it's always right after I start debugging right after starting uV2? I've tried to find ways to make it repeatable, like pressing RESET, cycling power, exiting and re-entering uV2, in various combinations and sequences, but I can't seem to make it repeatable. It does seem to happen every time I start debugging with uV2 for the first time each day. I don't think there's anything unusual about my pcb hardware. It's pretty standard... flash ROM at CS0-, shadow RAM (for the debugger) at CS1-, and program RAM at CS2-. There's no glue logic on the bus, although I do have a DUART (Philips SC26C92) on CS3-. Don't know if this matters or not, but I'm using the debugger in BSL mode, and based my project on the Phytec KC167CR sample monitor and BLINKY projects. Curious... Dave.