Jan,
It looks this file was in a bad state before PM modified it. I think it was created by ViewNX 1.0 on Windows, but there is also a MicrosoftPhoto rating in the XMP so I don't know its full history.
But if you revert the NEF in PM it will go back to the original.
It appears this corruption happened because of an IPTC update, not the capture times per se. IOW you probably had checked the option to update the IPTC/XMP time as well.
In the original file (i.e. after reverting), the IPTC tag was not properly inserted in the NEF's TIFF table. The TIFF tags are supposed to be in numerical order, and for some reason the IPTC tag (0x83bb) was written
after the Exif tag (0x8769) instead of
before it. This causes PM 4.6 to malfunction when updating the TIFF table (it inserts another IPTC tag causing the last TIFF tag and next IFD pointer to become corrupted). This probably didn't happen in PM 4.5.x because when it inserts TIFF tags it searches from the end of the TIFF table (not from the front as in 4.6) and therefore just updates the existing IPTC tag.
I will fix this in the next PM 4.6 build, but some software you are using is not properly writing the NEF file. Maybe this was a bug in View NX 1.0 (Nikon is up to version 1.2.2 on Windows).
--dennis