The ICM is heating up and failing on you. Some ICMs are poorly made and bad when they are new...but many fail when they get hot. You can have it tested at some auto parts stores, but my suggestion would be to ditch the BWD brand and get a Delco ICM...some are still available on e-bay for not a lot of money. The connectors could also be causing trouble when hot....so clean them up.
Keep the faith! Fieros CAN be dependable....carry a spare ICM and a small screwdriver and you can get yourself home if it happens again.
[This message has been edited by Gall757 (edited 06-23-2015).]