PPPoE over VLAN, problems

Hello

I use some Cisco an HP switches in my network.
On these there are many VLANs defined.
I have problems getting PPPoE working over VLAN it seems (mikrotik clients).
Everything else works just fine, but PPPoE seems to brake.
Anybody know if VLAN and PPPoE is incompatible?

PPPoE should work on VLAN.