We've heard of this issue from another user and it's in our short queue of things to investigate. We should be able to get to it soon, as we just released the newest version of JFBConnect, the first revision of our Virtuemart profile plugin, and will be releasing the updated Community Builder plugin soon.
The only bits we know about this specific warning is that:
1) It happens when you have the JomSocial profile plugin enabled
2) You're using Joomla 1.6
3) The JomSocial plugin is set to import the user's avatar (which still works as expected)
4) You have error reporting enabled in Joomla
Again, not sure what the cause is, but it's a pretty specific scenario, and we haven't heard of it causing specific issues (other than the warning), so it's not marked as critical. We should be able to have an update out soon though, once we focus on it and determine the issue.
Thanks for the report,
Alex