i dont think so . this is a linux kernel bug and since the version 3.10 to 3.13 use same kernel , so this problem existed in 3.x stable versions.
normis . still i am waiting for your reply
I talk with MTsupport already 2-3 month, but they do not see any problems , 
We have exactly same problems !
we have about 30 v2.9.x in network with pppoe, and work without any problems over 2-3 years,
and we have 2 v3.x with pppoe , and from all version of v3.x (we start with 3.6) problem are same,
but we have 6-7 v.3.x without pppoe and work normal !
We can not buy any more MT routerboard, because we can’t install v2.9.51, …
I must change this two v.3.x, because users complaints …
I do not know what to say anymore about v.3.x
… give us 3.14 with solution of this problems
RouterOS v3.14rc1 released but nothing about this damn problem in changelog 
I believe that for the present there is no any change. Momentarily i will use fixed directions in the problematic clients with private key even so much one finds the solution.
Regards
Unfortunately the problem still exist with no change in 3.14rc1 .
still this damn string shown 
unregister_netdevice: waiting for ppp121 to become free. Usage count = 61
The freeze still there on ROS 3.14rc1… Oh my…
As it looks like it v3.14rc1 walks worse than v3.13. PPPoE still freeze. I wait that the
mt team solves the problem for the close delivery.
regards
Currently it looks like linux kernel bug, we will check it and inform you.
Sorry, but if this bug is on the linux kernel i think that the mikrotik team will not be able to fix it. They can only hope that the kernel maintainers fix it first.
i think this problem for kernel developers is not as important as for mikrotik developers . mikrotik developers should try more and solve this problem before think about adding new features
The work priorities is unrelated between linux kernel developers and routeros. Yes, mikrotik should to try another solution, but if the problem is really on the kernel the fix is more complicated.
it seems one of pppoe problems solved http://forum.mikrotik.com/t/pppoe-and-random-queue-missing-problem/21413/141 . i hope this freeze problem solve also . i am tired of refreshing forum and checking my email to see solution .
Yes, how I see the problem stays, there was no solution.
I hope it will be fixed later.
I have upgraded My 2.9.51 to 3.14 after, but the PPPOE DIE problem was going on.
I had to downgrade to 2.9.51, in order do not have problems with my clients.
When it will be fixed? Who can tell us?
When it will be fixed? Who can tell us?
Guess it will be when MT do change the kernel. Googling around you may find that Fedora Core solved the “unregistered_netdevice” problem while other distros not. It is a bad bug and also it is very complicated for them to solve. But youre right, who knows? About 95% of our MT deployment are small pppoe servers to handle about 50 clients each and even ROS 3.4 that do less freezes (but some times it do) is a pain for our customers. Unfortunately, this minor amount of thousand people complaining about it does not take precedence on their priorities to solve problems. Who do even knows if it is on their “to do list”? Lets just hope and pray for this day to come asap…
this make us more nervous and they did not reply here
i heard this somewhere else . maybe it is better to write some of those links here for mikrotik developers .
in 3.14 the unregister_netdevice problem occures less (about 1 time per day) but still happens and still 3.14 is unstable
I had a similar problem here and, as a last desperate resource, exchanged hardware for a more powerful x86 platform (from Athlon64 to C2Duo) and the problem just disappeared. I just couldn’t believe since the Athlon was running only about 20% of CPU, now the C2Duo is using SMP and running about 1-5% of CPU… Maybe it’s a race condition in the kernel, who knows…
are you sure ? when you changed your cpu ? how long your mikrotik doesn not crashed ?
5 days, no crash.
But this is only my experience, YMMV. I don’t know if everybody that is having this issue have a similar hardware setup.
Since RouterOS is bound to the disk only, worth a try…
I tried your suggest with Core 2 Quad . with 4 cores now the cpu is 0-5 % ( most 0% ) but the unregister_netdevice occures MORE . i am confused and disappointed completely