Thx for your reply.
I investigated my problem further.
What I said already is that I have a 'RF MCE Remote Control' and I have configured it within EventGhost using plugin X10 medion with remote type Medion.
I am using currently the multitap functionality in which I have configured a SMS configuration.
I am using the YouTube plugin and when I'm entering for example abba, the digits are always processed, but the functionality of the multitap is ok (see screenshot).

- Multitap usage within youtube
You see here that I entered 'abba' and that the numeric key 2 is added 6 times (a=1 time pressed,b=2 times pressed)
I disable the windows service that is created by eventghost (X10 device network service), but then no keys are coming in anymore, which is ok. So, there is no other service running which is catching the keys.
Here is my eventghost configuration file.
I hope someone can help me, because I spend already some days investigating it, but I'm blocking.
I also enabled the XBMC logging, but I'm not seeing anything strange in there.
I hope someone can help me.
I am using Eventghost 0.3.6.1487 and the latest XBMC windows atlantis release.