Windows live messenger sharing folders randomly working

Hi all,
I am getting crazy about this odd situation:
I have been using windows live messenger sharing folders for a very long
time but, lately, they're acting strange.
Sometimes they work and some other don't. I am using them to share some
executables (encrypted to bypass the .exe blocking protection) but when I
tried to share a large file (400mb) the service stopped working.

I can read "trying to sync" or even "syncing" but nothing really passes by.

Tried to remove the large file and put a much smaller one to no effort...the
service will not work anymore. Yesterday the smaller files synced but when I
tried to share the large file...uhhhh...it stopped.
Is there any size limit for individual files?
Or, why did the service not start again when I removed the large files?

I have windows live messenger 8.5.1302.1018

Any help appreciated,
Stefano