Enabling WVGA issues

I am trying to run an LCD WVGA panel at 50 Hz......

bootargs=console=ttyS2,115200n8 console=tty0 root=/dev/mmcblk0p2 rw rootwait oma
pfb.video_mode=800x480MR-16@50

However, I end up with the following complaints during boot:

VFP support v0.3: implementor 41 architecture 3 part 30 variant c rev 1
fbcvt: 60Hz refresh rate advised for reduced blanking
fbcvt: 800x480@50: CVT Name - Not a CVT standard - 0.384 Mega Pixel Image

Console: switching to colour frame buffer device 100x30
clock: clksel_round_rate_div: dpll4_m4_ck target_rate 48000000
clock: new_div = 9, new_rate = 48000000

Running it with the refresh set to 60 seems to boot OK with DVI output (but is too fast for LCD)

I tried 50 Hz refresh without reduced blanking, but the boot hung after a complaint that the clock could not be set to the correct frequency.

Does anyone have suggestions here?

Thanks,

Keith