Latitude E5410 loses ethernet connection

I have two laptops with similar problem. After a while ethernet connection is lost (yellow exclamation mark with "no network access" sign). Sometimes it happens randomly, sometimes when I copy large amount of data over the local network. Problem is solved by restarting computer, but only for limited amount of time. System logs have nothing regarding this problem.

Wireless connection work like a charm.

I've updated BIOS to the latest, have the newest driver for NIC - still nothing changes. Other computers on network work perfectly, only these two have problems.

System: Windows 7 (32 bit)

NIC: Broadcom NetXtreme 57xx Gigabit Controller (driver version 15.2.0.5)

I would be most thankful, if anyone could point me in the right direction to solve this problem.