Have had this problem for the past week now.

TF2 constantly wants to validate, even if it's managed to complete it a previous time without any problems. It hangs there at 100% done for "1 of 1", though remains at "0 of 1" for the Steam Cache files.

I've followed the instructions on the support pages (namely, delete all the files bar a few and reload) and whilst it worked as a tempory fix, the problems returned again.

Any suggestions folks?

I had this myself not too long ago, i sorted it by doing a manual validate steam cache files and then restarting steam.

I usually get this after every tf2 update now, last time I had the same issue, coudnt get past validate. I tried starting tf2 a couple of times and restarting steam..fixed the issue somehow.

Oh for the love of...

Was playing it last night after having to restart steam to get it to work. Just logged into Steam now to play it after work and the bloody thing's gone and uninstalled itself.

How on earth xD

I've had this problem and the only sure fix is to uninstall TF2 and re-install.
=/