Not receiving e-mails!

Over the past week or two I've noticed a decrease in the amount of e-mails I've been receiving. I thought it was just a decrease in spam to start with, which I liked the idea of, but this morning after logging onto webmail to see what was happening, I realised that hundreds of perfectly legitimate messages have been received by the server but Outlook 2003 hasn't been downloading them for some reason.

I've tried disabling the spam filter, recreating the account in Outlook...I really would like to leave reinstalling Outlook as a last resort. The spam filter on the server prefixes culprit e-mails with "[SPAM]" so I can tell it's not filtering out many of the e-mails I've been missing for no apparent reason.

I can't work out if this is a problem my end or if something's up with the server.

Any ideas?

Thanks in advance

-Sam