Disappearing emails and attachments

Firstly check your rules or rules and alerts for reasons for disappearing emails. As for the "lost" attachments, no ideas.

I would urge you to backup your email and contacts and try setting up your acount again and import all back in and try to see if it's cured. Otherwise, uninstall and reinstall and get all the MS updates.

Hope this helps...

we need to know if you are on exchange or using outlook configured for the internet...
does your version of outlook offer Inbox repair? under tools probably.
sounds like corruption. is the mailbox pretty big?
you could set up a new profile just to prove it works fine in a new profile. if you export your stuff from the old profile and into the new one you may fix it as export/inport is 'poor man's' repair-often it will fix corruption during the process. got backups?

As to the 'disappearing' emails, check your 'Views' to make sure you can view all messages. You may have inadvertantly opted to view unread only or some other option.
As for the attachment issue, I'd suggest taking a look at the MS KB, http://support.microsoft.com/search/default.aspx?spid=928&query=attachments+not+shown&catalog=LCID%3D1033&pwt=false&title=false&kt=ALL&mdt=0&comm=1&ast=3&mode=a&x=12&y=12
Unfortunately, you didn't really give enough information to adequately define the search, so you might try a different search. However, there were a few results that looked promising. Good luck.