I know the pain... i have been through that situation recently...
And i also found a tool that makes this kind of debugging much much easier...
The Tool is "Flash-console" by google.
This tool has helped me a lot.. and i would ask every serious FLEX/Action Script developer to check it out...
I am still exploring all the possibilities and will update here if i find anything interesting...
Happy Coding.. !!!!!!!!!!!!! :-)