openform action was cancelled - why?!?

[Steve Hall]

Folks,

I have an Access front end to a SQL Server 2k back end.

The database consists of 5 main "record types" (many more tables than
this however) - Test Logs (TLs), 2 Test Executions (TEs), 3 Test
Reports (TRs), 4 Observation Reports (ORs), and 5 Change Reports
(CRs).

All TEs have a parent TL.
TEs can have child TRs, but TRs can be raised separately.
TRs can have child ORs, but ORs can be raised separately.
ORs can have child CRs, and CRs cannot be raised any other way.

For each record type there is a datasheet view listing all the records
of that type, and a form view to view the details of any one record of
that type.

Within each form view there is either a subform listing all "child
records", or a text box linking back to the parent (if any).

Now, I can go into a TL from the datasheet, and click on a child TE,
no problem. I can go into the TE from the datasheet, and click on a
child TR no problem. BUT if I go into the TL from the datasheet, then
click the TE, then click the TR, I get the good old "openform action
was cancelled" error - triggered on the docmd.openform line of the on
click handler - NOT in the form open event. What Im saying is I all
the "parent / child form relationships" work fine - but I get the
error when trying to move to a 3rd generation.

Any clues?

Thanks

Steve