iis server crashing on windows 2003 server for my web application of asp.net 1.1

hi,
i am having the server with windows2003 and iis 6.
 
on this server we are having a web application developed in asp.net 1.1 framework.
 
my asp.net application is daily getting crashing for every one to two hours.
 
only after i restart the iis server , the problems goes and after 1 hour , once again the application giving error as 'server application .
 

please give solution for this error.
 
thanks,
jagannadh