This coincides with some other problems that Buzzword users have been experiencing. I've learned in the past year that Manila's a hard program to run well when you're hosting several thousand weblogs and you don't know shit from Shinola.
I have begun a new mailing list, Manila Uptime, to document my efforts to bring the server up to the level of reliability I expect from Apache. I hope that we can rope some other Manila admins to the list, fix some bugs and find mistakes I've made that hosed the server.
I've seen that behavior on my server in one of two situations:
1--bloated data file and Frontier locks trying to load it into memory.
2--corrupt data file
Quit Frontier, make a copy of the directory, then take a look at the size of all of the root files. Consider writing a startup script text file that will save copies of all of the roots *before* they are opened. The script in system.startup.startupScript is run each time Frontier (or Radio) starts and in your case is looking for "frontierStartupScript.txt" in the root of the Frontier folder.
Write a short script to compact all of the non-app data files to see if that helps.