Copied from the SharePoint Dev Wiki as the post there was deleted:

Use the following to add an item to a list:

01: public static SPListItem OptimizedAddItem(SPList list)
02: {
03: const string EmptyQuery = "0";
04: SPQuery q = new SPQuery {Query = EmptyQuery};
05: return list.GetItems(q).Add();
06: }

Do not use SPList.Items.Add as this will get all items in the list before adding a new SPListItem.

1. Open regedit (start>run>regedit)
2. Navigate to HKLM>System>CurrentControlSet>Control>LSA>Kerberos>Parameters
3. Right click on the Parameters item and create  a new DWORD entry with the following:
   Name: LogLevel
   Value: 1
4. Close regedit
5. Restart the server

Errors will appear in the event log

Other Useful resources

http://blog.myitechnology.com/2008/09/troubleshooting-kerberos-issues.html