Yes, we use domains widespread over our model. In fact, as I wrote up here:
If I use the package with a blank Oracle 10g model, it loads the Entity properties form but it gives same error when saving domain for a field
if I start with a clean model, modify the form and then try to save a domain for an attribute, I get in the same situation.
Unfortunately not using the domains is not an applicable workaround for our case, as stated before we use them all over our model and we also export them to our ORM.
Hope it will be fixed in the upcoming version.
Meanwhile, I opened two other topics about issues I encountered re-customizing forms:
DataVirtualGrid "InplaceEdit" gone in TOAD 6?
PERAttribute custom property does not appear when customizing forms
Please give them a look, maybe there's something else to fix in the new version 