I don't mean to bump my own thread, but I found that both of our clients seem to have 1 file which disagrees with the checksum (or whatever you guys use to compare files).
The strange part is that after repairing this, simply launching the client damages the file again.
ie.
I verify my game cache, 1 file incorrect
I verify my game cache, no problems are detected
I launch the client
I close the client
I verify my game cache, 1 file incorrect
My friend seemed to have a similar issue, but there was something wrong with his installation (first time setup everytime) which I think is a registry error on steams part rather than the client.
We will (hopefully) test this again tonight, with 2 fresh installations.