Weird Timestamp URLs?

Hi there,

Hope this is the most relevant forum on Webmaster World to post this question in. I'll explain the issue...

GWT is showing a large increase in 404 pages on our site. The URLs looked very strange, so I delved deeper to find where these pages were linked from. The linked from pages turned out to be equally strange - and furthermore, I could not even find the link.

One of the developers here spotted that that the strange numbers in the URLs (1345870910000 and 1347970972000) appear to be timestamps. However, we have no idea a) why these pages are suddenly being found, and b) how they are being created.

I hope somebody will be able to offer some advice!

Thanks for your time.

Mark

[edited by: engine at 1:05 pm (utc) on Sep 27, 2012]
[edit reason] no specifics, thanks [/edit]