I've been having problems with heavy artifacting on seemingly random scenes in various MKVs that nobody else was having trouble with. they'd always occur in the same spots.
Experimented a bit to try and solve the issue. Switched to system drivers, etc. Turning off GPU Acceleration is what did the trick. Worked fine on my previous system though.
Windows 7, 64bit
Intel(R) Core(TM) i5 CPU M 450 @ 2.40GHz, 2400 Mhz, 2 Core(s), 4 Logical Processor(s), 4GB Ram
ATI Mobility Radeon HD 5470, 512GB ram
using the most recent drivers available, etc.