Ya the one I had trouble with was a Motorola - not a cisco. It wasn't an issue of getting nat to work, the problem was the unit would not aquire an ip address via dhcp. We eventually set it statically in the unit and all was well.
In the case of the ip debit machine, it had no way to set the ip statically, it forces the user to use dhcp. We had to use a Linksys router in between them. The router aw able to obtain an ip from the Mikrotik, and the debit machine was able to get it's ip from the linksys.
Both devices were working properly on the qube3. The leases table of the Mikrotik shows the mac addresses as being 'tested' then 'offered', but never bound - it just times out.