[ic] 500 internal error on checkout

[root]

i am getting a 500 internal error on checkout. after clicking the place order
button.
the order does get through and is placed in the orders database table, but  the
internal 500 comes up and no receipt is displayed????


can anyone help
i checked my error logs
and there is noting besides the usual 

203.198.84.94 cI8GIbLR:203.198.84.94 - [21/August/2001:15:56:29 -0400] chantel /cgi-bin/chantel/process.html search error: Limit subroutine creation: bad limit creation code in coordinated search, probably search group without search specification. at
/usr/local/interchange/lib/Vend/Search.pm line 703. >         

but i am told that is nothing ??? and i have been having that error being
reported since day one.

i have changed nothing in the shop. 
Just one day checkout works , next it doesn't.

help????

Ryan Snow.
Programmer
ryan@whoopersnetwork.com