GhostBSD is not corrupting your CMOS; if there are system issues involving the CMOS and Graphics card it is more than likely your BIOS. If your CMOS got corrupted there are issues with compatibility and/or video settings possibly instigating the BIOS to activate some type of trouble-shooting system that eventually crashes.
I have had similar issues with Gigabyte mother-boards where the BIOS will roll through different configurations in an attempt to get all hardware properly registered and running and get stuck where I would have to manually reset the BIOS settings and reconfigure them manually. It came to pass that I had a bad RAM slot, but that's a different discussion.
Neither GhostBSD nor its constituent system FreeBSD manipulate the CMOS or BIOS in any way; these systems could be used with specialized software to perform such tasks and FreeBSD may even come with tools that allow root users to engage said systems, but they themselves do not engage or normally allow access to the BIOS or CMOS for security and stability reasons.
CMOS is almost like the basic computer RAM for the BIOS and is reset or flushed at power off requiring a battery for persistence which may be another issue you could be encountering. If the battery dies, or is dying then you may run into issues where your specialized configurations are not remaining in memory and is evident by corrupted timing where the system clock always gives an incorrect time & date.
Conclusively: the problem(s) could be BIOS configuration issues involving incompatible settings, a dead or dying CMOS battery or failing hardware, in this case: either mobo or graphics card primarily, but could be memory too and is most likely not the O.S.
Solution: clean out your box/laptop, reset your BIOS to default settings, and pull all the memory but 1 stick and test the system for stability.