Haven't seen this error before, but what troubleshooting have you tried?
Detect and Repair? Scanpst.exe? New mail profile?

--�
Milly Staples [MVP - Outlook]

Post all replies to the group to keep the discussion intact. All
unsolicited mail sent to my personal account will be deleted without
reading.

After furious head scratching, Bluze asked:

| Unable to open or delete one specific reoccuring calendar item.
| Returned error: "CAN'T OPEN THIS ITEM. UNKNOWN ERROR"
|
| Can't seem to find anything directly related to this error. Anyone
| came across or has seen this issue before?