After long operation without problems, Outlook has, in the last week, come up with illegal operations whenever I select the Find a Contact box. It does not seem to be related to the Contacts file size (506 items - still there when I delete a couple of dozen), is Outlook 2000 specific (Outlook 1998 on the same file is fine) and I am not aware of any changes to the system other than installing MS patches (MS02-009 to IE5.5 is the only recent one). I am using W98SE with Office 2000 Professional.

Does anyone have any ideas?