Run an AC current through a rectifier, and you'll get DC with a very significant ripple. That could have an effect on the electronics downstream in a switching power supply.
In the abstract, a 400 HZ ripple should be easier to smooth out than a 50/60 HZ ripple (e.g. a smaller capacitor would be required). But it does seem possible that a system designed for 50/60 HZ and not tested at 400 would end up having problems at the higher frequency.