I put together a grid using Outlook style grouping, with about 30 choosable
columns. About a third of the columns have custom summaries, and about half
of these use custom Formulas in conjunction with an UltraCalcManager. It
works OK except for one problem.

When I change the grouping, or the sort order of a group, the change may
take a second or so (there are 6,000 rows in the underlying table) before
the grid appears to have updated. That is OK. But then the CPU keeps
chugging away for another 5 to 15 seconds. Worse, with certain groupings,
the CPU keeps going apparently indefinitely, as if it is in a loop. The UI
continues to be responsive, so something is going on in a background thread.

Does anyone recognize this issue or have advice on how to fix it?.