Even on the latest 5.1-5021 version of Synology‘s DSM I couldn’t get my Terratec Cinergy Hybrid XE working on my Synology NAS — the corresponding kernel module tm6000 would always generate a general protection fault on my DS414.
Today I upgraded to a DS415+ (with a completely different CPU), and the module still crashes.
So it seems it’s a real bug in the driver, not just a defect on a single platform (which can happen e. g. due to compiler bugs).
Update 2015-06-19:
Unfortunately Synology seem not very interested in this kind of problems. I repeatedly reported this issue, but all they replied is “Thanks for your report, we’re looking into this.” Even in the latest DSM release 5.2 the issue is still present.