Search not working - 500 error. - Joomla! Forum - community, help and support

i following error when search in joomla:

server error
the website encountered error while retrieving http://www.mysite.com/index.php?searchw ... com_search. may down maintenance or configured incorrectly.

i've tried reinstalling search plugin , module no avail. tried searching not find answer. have sh404sef installed when disable that, doesn't work appreciated.

running joomla 1.5.25 , virtuemart 1.1.19

thanks!