I'm not exactly sure what the technical reason for this is, but it appears to be the result of a change in Windows starting around Windows 7 (maybe Vista?) with regards to the graphics engine. A number of games have slow launching now in a similar vein, or other graphics glitches (like the flickery screen many people experience in Planescape: Torment on newer Windows versions).
Sadly, even GoG's efforts cannot entirely counteract changes Microsoft makes to the Windows core functionality. It is a fortunate thing that Oracle lost their case, as I expect in the future many "good old" Windows games will eventually only be viable to run in Wine on Linux as eventually Windows is quite likely to simply have moved on to a point that the games are simply too unhappy (Wine, by contrast, will rather reliably mimic virtually any version of Windows upon request).
