rabidrabbit :
what are your system specs and what setting are you running ARK on? it can be a monster if you let it eat all system resources. also test your RAM go look at MEMTESTx86 that should scan it and see if you have any bad RAM which would be causing your problem... but it may also be video ram issues what GPU are you using?
I run Ark on the lowest in-game settings, the specs on my GPU are
Graphics
Monitor
Name LG TV on NVIDIA GeForce GTX 560
Current Resolution 1360x768 pixels
Work Resolution 1360x728 pixels
State Enabled, Primary
Monitor Width 1360
Monitor Height 768
Monitor BPP 32 bits per pixel
Monitor Frequency 60 Hz
Device \\.\DISPLAY1\Monitor0
NVIDIA GeForce GTX 560
Manufacturer NVIDIA
Model GeForce GTX 560
GPU GF114
Device ID 10DE-1201
Revision A2
Subvendor EVGA (3842)
Series GeForce GTX 500
Current Performance Level Level 2
Current GPU Clock 405 MHz
Current Memory Clock 324 MHz
Current Shader Clock 324 MHz
Voltage 0.912 V
Die Size 332 mm²
Release Date May 17, 2011
DirectX Support 11.0
OpenGL Support 5.0
Bus Interface PCI Express x8
Temperature 33 °C
Driver version 10.18.13.6191
BIOS Version 70.24.18.00.66
ROPs 32
Shaders 384 unified
Memory Type GDDR5
Physical Memory 1023 MB
Virtual Memory 1024 MB
Bus Width 64x4 (256 bit)
Filtering Modes 16x Anisotropic
Noise Level Moderate
Max Power Draw 170 Watts
Count of performance levels : 3
Level 1 - "Default"
GPU Clock 50 MHz
Memory Clock 101 MHz
Shader Clock 135 MHz
Level 2 - "2D Desktop"
GPU Clock 405 MHz
Memory Clock 810 MHz
Shader Clock 324 MHz
Level 3 - "3D Applications"
GPU Clock 850 MHz
Memory Clock 1701 MHz
Shader Clock 2052 MHz