Home - Work link doesn't work but each works separately

I have iChat AV installed on both home and work computers, with different AIM names. Each works fine calling other people EXCEPT I cannot do video and audio (but can do texts) from home to work or vice versa. I usually get the "XXX did not respond" message. My two AIM accounts have the same address (mine) but their names are different, and I see home (or work) highlighted with a green video signal from work (or home). Very frustrating, as I casn video-call everyone else from home or work except my family!

Any ideas much appreciated.