I use a cookie to track login data on my system. This works very well except occasionally I am getting an invalid cookie. The pattern is always the same and I was wondering if anybody else has ever seen this cookie.

They look like this:
22d7a2a308000014||t=1252488988|et=730|cs=5uwjtc1f

And I get them quite frequently so I'm concerned about a compatibility problem. This is kind of security related since it is my login cookie being hijacked by some browser, bot, or some kind of spam creature. In any case if it is a proxy doing this that user would be unable to use my site.

They generally come from unique addresses.