[Case:]

i have mining rig with dual 6990s  for a tleast two moths now and for the past week it has been turning itself off after 16-18 hours of mining. Its been acting very strange i tried updating to 11.6 yesterday to see if that helps and it doesnt. Anyone know whats going on? 

Full spec:

Case: COOLER MASTER HAF 932 Advanced RC-932-KKN5-GP Black Steel ATX Full Tower
Graphics Card: 2x MSI R6990-4PD4GD5 Radeon HD 6990 4GB 256-bit GDDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card with Eyefinity
CPU: AMD Athlon II X2 255 Regor 3.1GHz Socket AM3 65W Dual-Core Desktop Processor ADX255OCGMBOX
Ram: G.SKILL 2GB (2 x 1GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) Dual Channel Kit Desktop Memory Model F3-10600CL9D-2GBNQ
Motherboard: ASUS M4A89TD PRO/USB3 AM3 AMD 890FX SATA 6Gb/s USB 3.0 ATX AMD Motherboard
PSU: OCZ ZX Series 1250W Fully-Modular 80PLUS Gold High Performance Power Supply compatible with Intel Sandybridge Core i3 i5 i7 and AMD Phenom
Wireless Adapter: TP-LINK TL-WN722N USB 2.0 High Gain
Harddrive: Seagate Pipeline HD ST3250312CS 250GB 5900 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive
OS: Windows 7 Ultimate 32-bit

My sapphire HD 5770 IGB runs at 100 degrees when i run the phoenix program at the clock core of 850 which is the default. Does anyone know why this is happening??

my setting on phoenix is

http://username@deepbit.net:8332/ -k poclbm DEVICE=0 VECTORS BFI_INT AGGRESSION=8 WORKSIZE=128