I've been able to narrow down (sort of) the problem somewhat - it doesn't appear to be server related, since it occurs with databases on two different servers, but it doesn't occur with all of the databases on the server. It seems to happen with one particular database on each of two servers. There are relationships between the two databases, but some or all (in various instances) of those relationships are also shared with other databases that aren't causing the problem. I've tried selectively removing items from the diagram one at a time to see if I can isolate the issue to a specific database item, but so far I've had no luck...
Any suggestions as to the next step?
DBA, Infinity Data Corp