I'm posting here, just in case other users are looking at this, as I've contacted rdl directly about the issue:
since removing omgwthnzbs from my rss feeds, the freezing still happens, but not lasting as long.
If I immediately check my logs after a freeze I see the 13 or so rss feeds all being checked at once.
I'm drawing a conclusion that hitting that many rss feeds at once might be the cause of the freeze.
The next step will be to reduce the number of rss feeds to see what is a reasonable number to check at once.
Or, alternatively, as a possible suggestion, is there a way to stagger the rss feeds so one happens each minute or even 30 seconds apart? - that would mean the program wasn't hitting up 6 sites with 13 api requests all at the same time.
I would also draw a conclusion that omg was making the problem way worse.
Thanks again.