I posted the other day about this issue but I have new information.
I have a Gravity Form that is using Aweber integration. When it is on it's own it works fine. When it is connected to Cart66 the Aweber integration does not work.
I discussed this with Cart66 developer support and here is what they said:
After looking closer at the code, it looks like both Cart66 and Aweber integration are using the same process to connect to Gravity Forms (via a hook). Because of this, both would prevent the other from working and it looks like Cart66 goes first in the process preventing Aweber from working. (if Aweber were first, Cart66 would not work). Unfortunately there is nothing that we can do to change this unless Gravity Forms comes out with a workaround built into their own plugin. The hook we are using is gforms_post_submission.