pppoe just freez

Hi there i have an RB500 and i use the pppoe server that are on the router with V2.9.51 everything works like an charm no problem.

I know upgraded to the RB600A and did the same setup but when the client connect with the pppoe it just freezzz after like 2-5 min, have tried v3.3 and 4.4 same result client have an Nanostation 2, everything work fine with the RB500, and advice?

Regards
Wesley