Event ID 46, Crash dump initialization failed can be seen in the Event Viewer, if your computer cannot log the error or create a dump file.

It also lists 909MB of System Error Memory Dump Files and 909MB of Debug Dump Files (same thing?), plus 3.39GB of Per User Queued Windows Error Reports.

One of our 5 64-bit / 12 GB servers is crashing. I'm trying to figure out why. It's doing a kernel memory dump right now, and the file is ~800MB in size.I loaded it up with WinDBG on another x64 ...

These are safe to delete. Depending on your system, you may also see entries like Previous Windows Installation (s), System Error Memory Dump Files, and Windows Upgrade Log Files.