I added a BUNCH of new checked in the 3.x version of dbWalker you're using, the greetings file is one of those new checks.
You can check this manually by looking at a call handler or a subscriber where it's barking about missing greeting files and verify that they are indeed missing. I'm betting big money they are. Yes, you'll want to clean them up first - you can do this automatically with dbWalker if you want. But be sure to check a few of the handlers/subscriber manually yourself to verify they are missing - this is just a situation where there a file name path saved for the greeting and that path does not exist - this COULD be legitimate if the handler was set for a recorded greeting and then you switched it to a system greeting and then the file as deleted externally - but that's not overly likely.
