With regards to your option 3 (blank screen), I get that with my 8642 when switching on for the first time using a universal remote. I am going from the 8642 through an Anthem D2 to a Panasonic TC-P54V10.
To get a picture, I hit the 8642's "guide" option on the remote, that appears (but the video picture is blank), I switch channels and voila I have a picture and all is good.
I get the blank screen issue too, but not consistently. What I noticed the last few times it happened is, when I hit guide to bring up an image as Kruginator described, it's always on the PVR channel (950), which typically means I finished watching a recording, erased it and powered off. So... the next time it get's turned on, it's technically not tuned to a signal - which may be causing the blank screen.
To test I changed to a normal station, powered off and then back on again - always with devices/inputs in same order due to Harmony remote. Couldn't recreate issue. Changed my power on settings for the PVR from "last channel" to a fixed HD channel to see if that solves it permanently. This box remembers where the recording last was even after changing away from a mid-way replay that is paused. Which was only reason I used "last channel" setting for anyway.
And I finally got fed up enough with signal drop outs and FFWD macro block issue that called Rogers tech support to complain. Did the typical unplug/reinitialize steps to no avail as expected and upon mentioning that many other owners of the 500GB box are complaining of same, he said was first he heard of it but escalated to Engineer team to resolve with a ticket. My guess is the HDD, as has been suggested by others, since we're only seeing it on the 500GB. Would be curious to see if any of those who did their own HDD upgrade from the cheaper 8642HD are experiencing same issue.
In any event, wasn't expecting a fix, but if enough of us call to complain they'll hopefully get on it and give us a new firmware update - and maybe a monthly credit or something! As after shelling out $600 for this thing, I'm seriously missing my 5 year old 8300hd rental which worked like a champ! But committed to switch to a buy decision when a new model came out, as Rogers gives full warranty and free upgrade to anything newer released in the first 2 years (which is basically the break even point). But now suffering early adopter woes...