I also wonder of this is related to
this (AdventureFrame) in which case greater minds than mine are already looking at something that might fix this as well.
No, the issue here has nothing to do with the Hatter Daily Deed.
Since version 17.6 released I not only downloaded it and today's most recent daily build but guess what: I only had windows and mafia running and still get the error
java.lang.NoClassDefFoundError: Could not initialize class net.sourceforge.kolmafia.persistence.AdventureDatabase
java.lang.OutOfMemoryError: Java heap space
Google leads me to:
java.lang.NoClassDefFoundError This exception indicates that the JVM looked in its internal class definition data structure for the definition of a class and did not find it. This is different than saying that it could not be loaded from the classpath. Usually this indicates that we previously attempted to load a class from the classpath, but it failed for some reason - now we're trying to use the class again (and thus need to load it, since it failed last time), but we're not even going to try to load it, because we failed loading it earlier (and reasonably suspect that we would fail again). The earlier failure could be a ClassNotFoundException or an ExceptionInInitializerError (indicating a failure in the static initialization block) or any number of other problems. The point is, a NoClassDefFoundError is not necessarily a classpath problem.
Indicating that we tried to load AdventureDatabase and it failed and later when we tried building AdventureFrame, it gave up.
In order to figure this out, we'd need to see why AdventureDatabase failed to load.
In your "data" folder, do you have adventures.txt, zonelist.txt, and/or combats.txt?
Delete them and try again.