That it the aspnet.exe recycling. It can take up to 20 minutes for it to reset itself and it may be coincidental that you were unlucky at the time it has reached it's maximum ram usage.
This can occur on any server, in fact I'm working with some network connection problems with my own server that are bringing up that error!! GRR..
If an administrator can see this problem, they can often log in via remote admin and reset the application, but it generally does rectify itself.
Not really a complete answer, but the other side is that you're custom dll has been incorrectly written, causing performance issues which also bring the server to a grinding halt. Which is why I don't let developers on my server. Custom Modules can do things to your server you never thought possible.
If it's local, you need to go to the task manager, processs, sort by alpha and look for the aspnet.exe - kill the process and then in some instances, you need to reset your web.config file, but first, I'd be removing those dlls to see if they aren't the cause.
All in a days learning!!
Nina Meiers
Nina Meiers