I don't know whether I have posted this in wrong place.
I just discover something to solve the problem and would like to share it to all of you.
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Originally I have the problem as the recent hot topic in MF plugin broken
http://board.jdownloader.org/showthread.php?t=10531
I have discovered some link originally not work that can become work now.
(Although the tittle of that hot topic said it is solved,some of the MF link still not work)

Some MF link shows available in the linkgrabber of jdownloader
but after added it, it just show "unknown filesize"
then plugin defeat will happen
I have some of the links having this problem.
the link have problem will like this

xxxxxxx is the file code of MF
yyyyyyy.zzz is the file name of that file uploaded to MF

....(mf web link prefix).../file/xxxxxxxxxx/yyyyyyyy.zzz

jdownloader linkgrabber grabs these links will show they are available
then after u hv initiated the dl.
It will show "unknown filesize" then the plugin defeat happened.
then if u open the link in the browser,
it will become
.....(mf web link prefix).../?xxxxxxxxxx
then grab it again in jdownloader, the link will be available and can be downloaded really.

I think the MF plugin can't correctly get the dl link of this kind of MF link

some of the links that showed this is work.
original link
**External links are only visible to Support Staff****External links are only visible to Support Staff**
**External links are only visible to Support Staff****External links are only visible to Support Staff**
after changing
**External links are only visible to Support Staff****External links are only visible to Support Staff**
**External links are only visible to Support Staff****External links are only visible to Support Staff**

[Jiaz]

fixed, will work with next plugin update