Before reporting a bug, try to make sure it's a bug in ARMbasic and not a bug in your own code. Try to write a small test that reproduces the problem you are encountering. Read any relevant documentation. If you show people that you have tried to solve your own problem, rather than immediately running for help, you will be more likely to find people willing to help you.
Be as specific as you can - "The HWOWM library function fails when it is called with a value of 1234" is much better than "It crashes".
Also describe your setup, which board, which PC OS and other configuration details.
The first place to go in the case you believe you've encountered a bug is groups.yahoo.com/group/ARMexpress
If you have isolated a compiler bug completely, and you have steps to reproduce it and a small piece of sample code, you can also file a bug report with tech support at support @coridiumcorp.com.
DO NOT file general "it doesn't work!" bug reports in the groups.yahoo.com/group/ARMexpress system. Only isolated, reproducible bugs should be posted there.