Well, let's put the next note here.
And the topic is: upgrade the firmware sequentially.
Today I've faced some problems with an Aten KL9116 KVM. I went to the firmware download page and have downloaded the last FW available (it was 1.0.081).
First, when I tried to upgrade it from version 1.0.068 right to 1.0.081, the window with the upgrade process stopped at 50% progress. Then, I tried to reset the device and restart the upgrade. But, even after I've got a message about the upgrade success and after the device reset, the firmware still was the 1.0.068 version. Then, I've got the previous FW (V1.0.069) and tried to upgrade with it - upgrade succeed. Then upgrade from V1.0.069 to 1.0.081 - successful again.
Unfortunately, the manual doesn't make it clear that the firmware should be upgraded sequentially. Hope this post will.