Outlook Express Malfunction

Suddenly I can’t highlight several postings in the newsgroups using the shift key to highlight and then combide and decode them. I’m runiing Win XP with all the service patches and critical updates installed. The processor is an AMD XP2200+ with 1.5 Gigabyte of PC2700 DDR memory available. Could anyone point me in the correct direction to solve this problem. It would be greatly appreciated.