Depending on the RDP configuration and graphics adapter hardware, screen artifacts and refresh issues can occur. Also some network devices, which are trying to "optimize" RDP bandwidth usage can cause issues. To troubleshoot those issues, try to disable the following settings:

On the Performance settings page , make sure you have disabled the following:
  • DirectX
  • Desktop Composition (Aero)
  • Visual Styles
On the Advanced settings page , try to disable the following:
  • Bitmap Caching
  • Compression