[ubuntu] 14.04LTS Network speed problem?

Dear all I am trying to figure out a problem with network speed on Ubuntu 14.04 (Desktop x64).

Using a system with RadiusDesk installed and using coovachilli as hotspot I am getting a strange behavior....

When a LAPTOP client is coected on the Ubuntu when the link speed is 100ΜBps speed tests are ok (backbone 300Mbps)..

When a LAPTOP client is coected on 1000Mbps link speed I have normal speed downloads but NO or very slow upload (10-20Kbps!!!).

Trying different NICs and whole PC's didn't change anything... The setup is pretty simple with no strange tweaks...

Could someone guide me from where to start?

*Also trying the same setup from readymade VM image (on windows) has the same results!!!

BUT if the client is a MOBILE device (through an AP) upload speed is always normal according to the air-speed coection.

Thanks in advance!

P.S. My main NICs are Intel Pro gigabit desktop adapter (e1000 driver)