The issue with VMware not booting Lx 4.3 is known and discussed here.
People in the contributor group use VirtualBox for testing thus we know Lx 4.3 and other versions of OM Lx do work in VirtualBox. We would need more details about your situation to problem solve anything.
The screen-shot shows that on OM Lx 4.3 host machine I have OM Lx Cooker, Rolling, and 4.3 VM’s. I use them all every week for testing various things. On the right you can see settings for one VM so you can see what works here.
You will need at least 2 GB memory and 8 GB disk space for OM Lx in VirtualBox. I would recommend 15 GB of disc space if you can do that. Also things to look at are Graphics Controller where VBoxSVGA works here but other folks report using other settings for that. Also look at settings under Paravirtualization Interface, sometimes different settings work for some people. The Graphic Controller is more likely to be a problem than Paravirtualization Interface so I would play with Graphic Controller first.
Problems in Virtualization software get complicated. We are talking software that can operate on almost any host operating system and ideally will run almost any operating system. To fix a problem we need something to work on, something more that does not work.