facebook login gives error - urgent (it's at my live site)

hello,
since now everytime I want to login with facebook the following error occures:
first of all it takes forever to load and then it says:
Warning: Division by zero in /components/com_community/helpers/image.php on line 146

I only get that when logging in with facebook. usual joomla login is working without problem. it's really urgent because it's at my live site. what causes this problem? and how can I solve that?

joomla 1.5.23 - jomsocial 2.2.4 -jfbconnect 4.0.2 (but I'll upgrade to 4.0.3 now)

my browserbar is showing: /component/jfbconnect/?task=loginFacebookUser&return=L2NvbW11bml0eS9yZWdpc3Rlci5odG1s

edit: update to 4.0.3 doesn't solve the problem. But I can see in the admin that the users are "connected" - but as written above they come to that error page and not to the frontpage.

thanks alex,
when turning off avatar the login is working.