Just stumbled across this thread while doing some Googling, I've had an HS324 Command for a couple of years with a viewfinder display issue which I'm fairly sure is caused by a fault in the LCD screen. For the first 10 minutes or so of being powered on, the screen has noise in the form of horizontal white lines that progressively get better and eventually disappear. When plugging in an external display to the hotshoe port, these lines aren't present. Hence my thinking that it's a fault with the LCD screen itself.
Does that sound sensible, or do you think the issue could be more serious? My hope is that it's just a quick fix to replace the QVGA LCD screen with a generic one.
I'd really appreciate any advice you might be able to give - hopefully you're still around and I'm not being too rude by replying to such an old thread!