If they block specifically YM, then there is nothing that can be done. With Socks Protocol add your ISA server [the same proxy provided in IE LAN settings] as the IP address and add 1080 as the Port. Try both of them, Socks 4 & 5 and hopefully it will work, not unless they define a role there to block YM, then nothing will work and Meebo would do the job :)
If they block specifically YM, then there is nothing that can be done. With Socks Protocol add your ISA server [the same proxy provided in IE LAN settings] as the IP address and add 1080 as the Port. Try both of them, Socks 4 & 5 and hopefully it will work, not unless they define a role there to block YM, then nothing will work and Meebo would do the job :)