I've found a certain combination of rules (when using inheritance) that causes drools to throw the following exception: http://pastebin.com/xxq5ZtAC

The rules that cause this exception to occur can be found here: http://pastebin.com/wM6rWY8L

I've simplified my original rules down to the lowest level of detail that still throws the exception. The exception is no longer thrown if I:
1. Don't use rule inheritance
2. Don't have an or statement
3. Don't reference an LHS defined variable in the RHS of ruleB