S7 Connection aborted!!

Hello people.
Iam getting the following error.

I clikc ok and try again and it works for a short period of time.
I'm using PC adapter USB type with this configuration:

the plc has this configuration:

Any ideas of why I get disconnected so often??

thanks

Ideas:
Extreme noise.
No ground.
The USB adapter may be defective.
The MPI port may be defective.
The cable may be defective.
There may be a conflict on the PC with the USB adapter and some other device.
If the PC is supplied from another source than the PLC: Too big voltage difference on the "ground" of the two systems.

Things you can try:
Switch to DP and go online via the DP port.
Change the S7 CPU.
Change the USB adapter.
Change the PC.

If nothing more is connected to the MPI port, set the "only master on the bus" flag of the PG/PC interface. This may help also.