Email Address Resolve (Auto Name Check)

I have user running Outlook 2000 on a Win2K Pro machine. SP1 for Win2K is loaded as is SR-1a for Office 2000 that OL 2000 is part of. Occasionally, his computer Outlook app will hang when he types in a name and Outlook tries to resolve that name to an address book entry. It doesn’t happen all the time and, at least initially, there isn’t much consistency to it. I do NOT know if the hangs occur when it is trying to check a name that may be in the Server store or in his Outlook Contacts folder.
Help is appreciated – Thanks!