I've been having a problem too, with PitBull and ArkInventory. I read here, decided to diff the AceEvent file. Seems PitBull's AceEvent is designed to work with 2.1, and may potentially alter some functions upon which ArkInventory depends.
*hint: the diff file is bigger than the AceEvent included in AI*
And, if I read right, Ace2 uses the newer version, which is the one in PitBull. AI depended on certain functionality in AceEvent which has since changed.
I may have mistaken the Ace2 memory concerns page... though, but I think it's how it works.