Problem with os_dly_wait() and printf()

Hello,

I'm using LPC2119 microcontroller and RV30 with RTX and ran into several problems.

1) If I use printf(...) inside tasks and use os_dly_wait(...) then as soon as context switching occurs then os_stack_overflow() is called. I tried to set up different stack sizes inside startup.s file but it didn't help a bit. I tried to run the same code inside simulator and it works OK without any stack overflow (which I was getting if I didn't include tsk_lock() and tsk_unlock() around printf(...))

2) If I get rid of os_dly_wait(...) calls and have two tasks running, then if I use printf with this kind of code:

int test = 10;
tsk_lock();
printf("test value: %u\n", test);
tsk_unlock();

Then the task, which ran that line of code, will get stuck including not context switching. I didn't get any stack overflows that time but it looks like it gets stuck when it tried to do a context switching. If, on the other hand, I put code like that:

tsk_lock();
printf("test value: %s\n", "just some test");
tsk_unlock();

Then it switches just fine. Thanks in advance with any suggestions or explanations, Alexei