printf not working

I’m doing “printf” from a kernel (and compiling with dbg and emu), but it doesn’t print anything. The weird thing is that I have two different kernels, one that prints this and one that doesn’t. Is there any timing issue I need to consider?
Sorry for not posting any code, but I don’t think it is useful since it isn’t self contained.
Anyone else has problems like this?

Thanks

EDIT: nevermind, stupid bug which resulted in 0 threads, so no printing =b