I am having a similar problem that this user was having: http://userproplugin.com/userpro/forums/topic/profile-picture-of-user-not-showing-up-in-multisite/, however, it does not look like a solution was posted.

Mine possibly appears to be a TimThumb issue and it is worth noting I have chmod’ed the lib folder and all the folders inside of it to 777, but still the profile images are not appearing. So I’m lost and looking for support.

Also, when I look at the image path/url of the avatar it’s: http://type.is/ext/userpro/lib/timthumb.php?src=%2Fwp-content%2Fuploads%2Fuserpro%2F1%2F52ea67e6ce0cd.png&w=80&h=80&a=t&q=100

It is worth noting, I am using a WP Multisite Sub-directory setup as well if that makes any difference.

Site link to issue: http://type.is/profile/type/

Screenshot: http://imgur.com/EGxwgWK

A TimThumb error has occured
The following error(s) occured:

Could not create the index.html file – to fix this create an empty file named index.html file in the cache directory.
Could not create cache clean timestamp file.

The error is written above, If you can’t correct it – I can do it for you, I need FTP details and please mention the thread URL when contacting me by email