I hope I've caught you before following Simon's advice Lona
What has happened is the new driver has defaulted to a different refresh rate than your old driver.
All you need to do is the following:-
Go to Control Panel,
select Display Properties,
go to the Settings tab,
click the Advanced button,
select the Adapter tab,
change the Refresh Rate selection to Optimal
click Apply
(I'm assuming you are using Windows 9x, it's slightly different in XP)
Hope this helps