In the pastjoomla 1.5.0 installed fireboard1.0.4stable successfully.
Joomla1.5.6 installed fireboard1.0.5RC, fireboard1.0.4stable installation has also made the same error 500:

The server encountered an unexpected condition which prevented it from fulfilling the request.
The script had an error or it did not produce any output. If there was an error, you should be able to see it in the error log.

Upload again extracting after the installation ,same error. Should not be a time-out, because I installed bigger Virtmart of 1.9M has gone smoothly.

This is why ? I contacted hosting supplier, they kicked the ball to the fireboard here.

what to do? It's urgent! Thanks