I really would like to run the native resolution of the laptop, that is 1400x1050. That's also the resolution radionfb selects by default (and it works).
Am I doing something wrong or is it a bug?
It seems that your desired mode (1400x1050) is not in /etc/fb.modes
For TFTs I used to boot with vesafb and then type fbset to get the correct timings for the TFT, but unfortunately, your VESA BIOS might not have a mode number for your non-standard 1400x1050, and if it has, it would be annoying to find it out. There might however be a tool to query VESA modes.
maybe searching the web for the correct timings and editing /etc/fb.modes is easier.
Andi