Sad but true, I've spent all of yesterday and today tracking down a memory leak that has been crashing dedicated servers and causing the game to slow down over time. Memory can be a tricky subject as there are different scopes, or levels, of memory, not all of which you can see and track as "managed" objects. I've identified the majority of the problems and am working on implementing fixes, but wanted to get the word out there first as I know some people have been having the server go up and down frequently this past week as well as the game slowing down when traveling long distances.
Should you be experiencing the game slowing down over time, returning to the main menu is not the way to reset the memory, you need to save and close the game completely. Sorry if this has caused anyone trouble, and hope to have a fix up tomorrow!