Route generator using incorrect host

Hi there,

Two times in the last three months I've had Rails start serving up
some links as <another site>.com/page rather than mysite.com/page.
The are sites are completely unrelated to my site, and I have no idea
why it did it. The first time it occured, the other site was
google.com. The second time it was tragicallynull.com. Sadly I can't
remember how I resolved it the first time, and the second time it went
away after I deployed some recent updates I'd made.

Any any know why this would happen, or what might cause it? Perhaps
even some tests I can run? I'm not even sure how to reproduce it at
this stage.

Tim.