WEB SERVER THROW OUT OF MEMORY EXCEPTIONS

Error: System.Web.HttpException: Exception of type System.Web.HttpException was thrown. ---> System.OutOfMemoryException: Exception of type System.OutOfMemoryException was thrown.

When my website  users access the above message is thrown.

this is happening because one of my users had accessed his favorite products page, which has been resulting time out, But this also resulted the above error for all the users who wants to login and who are already browsing.

This is happening only for one users who has like 1000 products in his product page, but why is it resulting in time out i dont know, we are using xslt to convert the xml file and showing his favorite products. We are using preceding::sibling in xslt file to filter the products category wise.

i can post my code, if you want.

Could you please tell me what is happening.

Thanks advance.