sysryn: Actually it's a known issue with any 64bit OS and the game (according to official forums). Most of the problems were reported by CD users and it carried over to Steam as well... Hopefully more people will reply and confirm that GoG is actually free of this.
I'd buy it again in a second if it works.
Dragonlightz: Unfortunately, the memory leak issue isn't exclusively on Steam. Sacred 2 had this issue since launch years ago due to a rush job by the developer under pressure from the publishing company. Depending on which class you play, you can get 2-4 hours of gameplay before it simply crashes. The golden rule for any RPG is save often! ;-)
Many problems were fixed afterwards by Ascaron, including receive a ctd when using the monoliths. Since patch 1.34 there were no real problems anymore. However, with Ice & Blood new bugs were introduced and some old ones returned. Deep Silver did nothing to fix it, since they took over the franchise after Ascaron filled in for bankruptcy. Latest patch was 1.65.2 and only fixed a problem with the chat window.
I have the dvd version myself of both Sacred 2 and the expansion. Played it without any crashes and that was with the vanilla version, patched up to 1.65.2. Played then with a high elf, seraphim, dryad and a temple guardian.
Not sure which version that of GoG is.