I have not tried running that old of an icq client with the newest inuse protocols, so i will have to guess it just wont work any longer. possibly due to changes in the server, from a TOC to the newer OSCAR login server, which is also used for AOL IMS.
you might be able to use it, cant say for certain. But make sure the password and UIN are correct. if it does not log you in, then you possibly can not use it, plus i would not want to use it, since when they did the change over from protocol v5 - > V7, i never got offline messages, Plus the newer servers hold contact list on the server side, which is a plus, dont need to back up your contacts anymore.
you might have a problem with 2 versions of ICQ.
maybe just try an alternative to icq, which there are plenty in the pinned topic to chose from