Terminating app 'NSImageCacheException'

Hi all, I've been struggling recently with a strange problem and haven't been able to find a solution yet.

Basically, what's happening is that I'm unable to open a certain app only when I'm using a certain network connection, and it seems like every time I try I end up corrupting the program itself.

The app in question is my League of Legends installation, and basically what happens is the regular blue and gold 'L' icon will bounce once in the dock, disappear and get replaced by the App store 'A' made of pencil/paintbrush/ruler on a blank sheet of paper. I then get a problem report for UserKernel pop up, with a huge wall of text of which the most relevant section seems to be this:
*** Terminating app due to uncaught exception 'NSImageCacheException', reason: 'Cannot lock focus on image <NSImage 0x72662b0 Size={0, 0} Reps=(
)>, because it is size zero.'

From then on the UserKernel itself seems to be corrupted and can only be fixed by replacing it with a fresh UserKernel from a reinstalled version of the game.

Now the most annoying part about this problem is that it only happens when I'm using a certain WiFi network. The network is moderated by Barracuda Web Filter, so at first I just thought it was some network administration put in place to prevent people from gaming on their internet connection. But if that's the case, how is it actively corrupting my files, and why can't I find any correlation between the web filter and error message with a google search? And if it is the case, is there any work around I could try?

Please let me know if there's any other information I can supply to help solve this, and thanks for your time.

 

Got an update/sneaky bump with more information.

I got the idea to try opening the launcher with one network connection and then swapping to the problem network and launching, with very interesting results. I am able to log in, open the store, (Haven't tried buying anything but I'm able to browse with no problems) and participate in games, but can't seem to connect to chat at all or view my friends list. Not sure what the implications of this are, but I'm wondering if some specific port-blocking could be responsible? Still confused as to how this could manage to corrupt my installation though.