Problems with the powered USB hub

My problem is that when I plug the USB devices into the 7 ports powered USB hub sometimes they don't work. I can use them OK and suddenly, the mouse is dead. Or everything that was plugged into the hub. Or I use a 3G phone as a modem connected to PC through USB hub's port. And I lose a connection and every time I have to unplug and re-connect and then connect again to mobile broadband ISP.
And its not after any event. Just all of a sudden. Then I had to unplug the hub and put it back etc. Its a pain to do it every 10 minutes. But sometimes everything works OK for hours.
I don't know...I bought a hub here in Sweden. And its not exactly cheap 250 SEK which is roughly 25 Euro or 35 US$. Its a metal hub. And it gets warm, but not too warm.
I use Windows7 Pro. And I disabled power management options in root hubs and in the hub itself.
Also I went to advanced power setting and disabled "USB Selective Suspend"
When something is plugged directly into the laptop's USB ports, then those devices work just fine. Its only when I plug them into USB hub. Frankly, I regret that I bought a laptop with only 2 USB ports. If I knew that the USB hub is such a pain, I would have only gone for 3 USB ports laptop. And also, I noticed that it doesn't really matter if I plug the USB hub into power or not. So maybe its not even a power issue to begin with.
I get Windows errors that USB device is not recognized and then I see an unknown device in Device Manager. It happens often when I connect an addition device into the USB hub.
We only have a desktop at home (another PC)...you think it's worth trying the hub on a desktop?

 

Have you tried using a different cable between the hub and the laptop or between the devices?

 

Well, I can't use a different cable, because it's a mouse and a keyboard that are connected to the hub, so there's no way to replace the cable...As per USB cable...no I haven't tried that...maybe I'll try that if I found another cable

 

Frankly, I don't think that overheating is an issue here...
A while ago, I was using the hub and everything worked just fine. And the temperature of the hub didn't make any difference or whether the device was getting an external electric power.
My impression is that the reason why devices that are attached to the hub disappear and therefore stop working is because for some strange reason they don't get enough power, REGARDLESS of whether they hub is powered itself or not.
I will tell you what exactly happened:
I had a 7 port hub connected to the laptop and I had in the beginning a keyboard, the mouse and 2 flash drives connected to the hub.
After that, I had the keyboard connected to the laptop's USB port and the hub was on the 2nd port.
Then I disconnected the flash drives and had a web cam, keyboard and 3G USB modem connected to the hub.
I went to the device manager and checked the propertives of 2 (?!) hubs that appeared in the list of the devices in PC.
In the 1st hub it was written:
The hub is self-powered. Total power available: 500 mA per port (?)
Attached devices:
USB Composite device 500 mA
USB Composite device 100 mA
2 ports available 0mA

In the 2nd hub it was written:
Generic USB hub (4 ports???) 0 mA
Logitech cam 100 mA
2 ports available 0 mA

Then I got the 3G modem CONNECTED to the ISP.
RIGHT AFTER that the keyboard died.
I also got a connection error in a modem (excl. mark in a task bar-No network access)...
Then I re-checked the previous generic hubs' properties.
In the 1st I had:
USB Composite device 500mA
USB Composite device UNKNOWN
2 ports available 0 mA
In the 2nd I had:
Generic USB hub (4 ports) 0 mA
Logitech cam 100 mA
2 ports available 0 mA
3G modem appears connected, but not operational.
I think that it was simply disconnected and then reconnected right away by the system...