Update
Well it's sort of working... I throttled back my RSS harvester to one thread, and that seems to have stabilized things... When it's running flat out there are bursts where I'm simultaneously pulling RSS items from 20 or more sites at the same time and adding them to the database... all this activity is (I guess) what was making the server seize up.
I reused Syndicache, my RSS to NNTP gateway, for this project, so that's the code that's pulling down the items.. there's a separate component that collects to blo.gs and takes the ping data from there and updates the database to queue an update of a feed..
As for why the server is crashing, I can't really say.. I still think it's hardware, but doing less I/O seems to have stabilized it.