I did some cursory searching and couldn't find another similarly named mod, so I assume Boggart is referring to my mod, Useful Summoned Creatures. There are a few things I would like to point out. First, I updated the mod a few months after its initial release with additional scripting checks to ensure better compatibility with other mods. If you haven't already, download version 1.1 http://planetelderscrolls.gamespy.com/View.php?view=Mods.Detail&id=7626 and give it a shot; it may resolve the issue with Gavyn.
Second, it was my first attempt at scripting. With no modding experience and very little understanding of potential issues/conflicts, I chose the simplest approach I could find. This meant attaching scripts to the summoned creatures themselves (a script for each creaturename_summon objectid). While I didn't change the creatures' properties (the fight/flee/alarm/hello/damage ranges/stats/etc. remain at their default values), my simple approach, though it works well by itself, is generally not a good idea when considered as part of a larger mod ecosystem. Now, I did try to minimize potential problems with additional checks in the scripting, incorporated into version 1.1, but its fundamental design may prove difficult to work around.
Partly to ensure compatibility with other mods, as well as add further features, I am completely redesigning the mod from scratch. The new version will not modify
anything found in vanilla Morrowind while still offering the prospective conjurer a bunch of nifty new features through scripted spells. Given these circumstances, please don't spend too much time working on it if the bug turns out to be a conflict with my mod. If there is one, it's probably because of how I designed my mod, which will no longer be an issue in later versions. If you have any questions about Useful Summoned Creatures, please feel free to pm me or post in its thread http://www.gamesas.com/bgsforums/index.php?showtopic=1007659.
Of course, if Boggart was referring to another mod then please excuse me while I quietly walk away, trying to act as casual as possible
.