first:
-download pbsetup.exe
http://www.evenbalance.com/index.php?page=pbsetup.php
-delete pb folder
-run pbsetup.exe - chose game - pick game instalation folder - hit check for updates (game shuld be off all the time doing pbupdate)
it will give you the most recent pb you can have
also after all above you can type in game console /pb_cl_enable and hit enter
second:
-almost all servers have their specific pak files for sounds,weapons,maps... no way to bypass this. if downloading is slower than your connection type /reconnect in console while downloading and hit enter (most of servers download speed is 200-900)
-you might also look at servers www for packed pak files =)
if you will have more problems copy to this forum thread exact error msg or paste a screen shoot (somoeone said one picture may tell milion words=)