To enhance reliability and performance on shared servers, every application pool is limited to use 64MB of physical memory. This is more than enough for an average web application. Also, this protects all applications and users on the server from suffering performance and reliability loss, due to the huge memory consumption of a corrupted script. Reaching this limit will cause an automatic recycle on your application pool. This means the restart of the underlying w3wp.exe process of your application.
As a side effect all application and session variables of your script will be lost!
Please check out our Scripting best practices knowledge base article for general guidelines on how to fix your problematic script.