Yup - I've been getting it too - though only for the past 2 days - 1 day mainly.

There are several possibilities & as usual the less paranoid & most boring are usually the reality  8)

Possibilities in order of likelihood

1. There are hardware/software problems (always temporary) in the immediate network of our hosts.
2. Server problems. Our main server is pretty full with 2 weeks of log files - causing the memory problems as swap memory cannot access the HD to the extent it would like .... (I'll run logs & clear out later so that will cure this if it's the culprit)
3. Local area DoS attack. (.. Happens.. )
4. We always have several people who don't like us. Any one of these can launch attacks at any time. They run the risk of being caught as all unusual activity is logged & stored. We also have tracing software installed (after warez guys hacked our box several years back..)- a bit like paint bombs in cash boxes..
5. We are being targetted by aliens. (almost definitely - Androids are rumoured to hate FS fans..)