Helen,
During the last few days OE has 'removed access' to all attachments received saying that they are 'unsafe'. As they have been sent by reputable organisations.
Are you
sure that they are from reputable origins ? There are a number of viruses about (Klez, Yaha, GIbe/Swen, etc.) that forge the sender address
precisely so that you think that they come from a "trusted source".
You don't say which version of OE you are using, but you should checkout the following security alert from Microsoft:
MS03-014 : Cumulative Patch for Outlook Express (330994) 