just for the record: avoid triggers, they are evil.
They are a tool. They can be used well or used badly. When used badly, blame the developer, not the tool.
Gail, you are right (as usual).
But triggers, cursors, denormalization and other DB tools are misused most of time by developers.
Cannot remember last time I found a trigger is not wrong used to implement a business logic better to be left in the application.
As a developer I try hard to put that tools to good use, only.
John, if you must stick with that application as it was made you are right to take extra caution before changing anything.
I also suspect that line is not the problem.
Make some profiling and keep a eye in that inserts query plan.
A spare server and a DB backup can be great to explore and test some solutions.
I hope you find the culprit and fix it (and share it at the forum).