The Motion Eye on my TR5GP stopped working for no reason last week as well; when I ran Smart Network Capture or MSN for a video conference, Motion Eye showed only either a completely black screen or black with video snow.
Fortunately, I had still 3 days of warranty left, so I took it in to the local Sony service center. After I told the representative that a large number of TR owners on this forum are facing the same problem, she admitted that there had been a large number of TR owners here in Singapore who had brought in their TRs for the same reason, and that the local office has already raised the issue to Japan.
Personally I believe it’s a hardware issue.