Squares around light sources, how to remove?

I don't have weak search fu, I have no search fu. I could swear I once read something about fixing the problem of the weird boxes that appear around light sources in game. Can someone point me in the right direction, or help me with the advice directly?

If it is relevant:

Model Name: iMac
Model Identifier: iMac7,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2.8 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache: 4 MB
Memory: 2 GB
Bus Speed: 800 MHz
Boot ROM Version: IM71.007A.B03

Chipset Model: ATI,RadeonHD2600
Type: Display
Bus: PCIe
PCIe Lane Width: x16
VRAM (Total): 256 MB
Vendor: ATI (0x1002)
Device ID: 0x9583
Revision ID: 0x0000
ROM Revision: 113-B2250F-219
EFI Driver Version: 01.00.219
Displays:
iMac:
Resolution: 1920 x 1200
Depth: 32-Bit Color
Core Image: Hardware Accelerated
Main Display: Yes
Mirror: Off
Online: Yes
Quartz Extreme: Supported
Built-In: Yes
Display Connector:
Status: No Display Connected

---

"Hmm, I guess I'm not as omniscient as I thought" -Gavin Runeblade.
I can be found, outside of paragon city here.
Thank you everyone at Paragon and on Virtue. When the lights go out in November, you'll find me on Razor Bunny.

Do you have the same problem on the Training Room?

---

Manga @ Triumph
"Meanwhile In The Halls Of Titan"...Titan Network Working To Save City Of Heroes
Save Paragon City! Efforts Coordination