Can’t open jpeg’s in Outlook Web Access

I can’t open JPEGS through Outlook Web Access. I have Exchange 5.5 SP4 loaded. I can open Word and Excel document attachments but not jpegs. It happens on XP, 2000, and 98 boxes with IE 5 or 6. If you save the attachment to the desktop, Microsoft Phot editor says it can’t determine type, even though on the desktop, the icon is exactly like a regular jpeg icon. Anyone seen this? Help!