"abilities cannot stack" message

[Professor Death]

Last night upon logging back in after Shadow reset the server I received two messages as noted in this report title. One was after casting a Bull Strength and the other after Endurance. Checking the character sheet, constitution was lower than it should have been. I tried unequipping and reequipping a +CON item and that fixed it. While this bug was occurring I also experienced the little red status icon indicating artificially reduced constitution. Despite the log messages about strength, it seemed unaffected and Ferrous does not have any strength boosting items that might have been in conflict with the Bulls I cast.