This sounds very similar to an issue I was having. After a number of exchanges with Humax support to try different things I replaced the HDMI cable (the one bundled with the HDR) with another (previously connected to my PS3) and thus far seems to have fixed this issue.
I had checked the cables were firmly seated and I was also using the latest software, although I have had this issue with all versions of the software.
Interestingly I have reused the cable for my PS3, with no obvious issues.