Item Creation Error

When I tried to create a Purchased Item, I got the following error:

	FND-FND_EF_MR_UNQ_SINGLE_SEG (FND--1) FND-FND_EF_MR_UNQ_SINGLE_SEG Cause The message, FND-FND_EF_MR_UNQ_SINGLE_SEG, can not be accessed. Action Report this problem to an administrator.

What triggered this and what does it mean?

Thanks!