access blocked

i upgraded from 98se to xp home ed. Since then every now and the i try to access different links (i.e. the help button in hotmail, also in hotmail when i click on the ‘show all’ link to display my address book)..i have a new optical mouse but i only changed from my old mouse thinking it may cure itself..but i still have the problem…when i click on these a red circle with a red line appears…like a ‘no smoking sign…any suggestions…thanks