This problem occurs when running the Arahpaint CAD/CAM program in a virtual desktop with X11Vector Graphics disabled and the pack method in the proxy extra options set to bitmap.

The display agent log reports errors like:

FrameUnpack: ERROR! Invalid message size 4671483.

Such program makes complicated raster graphics which cannot be easily compressed, with a resulting size quite big that sometimes exceeds the current size limits. Frames are therefore rejected by client side with the error above, making the session to freeze from time to time.