I set the upload limit on my LimeWire to 10 kb/s. When I set it it´s applied correctly but after some minutes it raises up to about 20 kb/s.
When I go into the preferences again and re-set the limit the whole thing starts again (goes to 10 then increases even if still set to 10).
What can I do about this?

Well ... I cannot set my upload limit below 10.94KB/s Are you setting it to the absolute minimum. Prerhaps you are not pressing apply > ok after setting it.

I would ask: you why so low?, but I see you are also posting a technical question of subjects beyond the minds of mere mortals so I shall assume you are exploring the capabilities of Limewire

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Isn´t pressing "OK" after setting it okay. The problem is that for some time the limit works great but then it´s ignored.

you have to press apply first.

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To get Phex Click on the Fox