Tvheadend

Hi

I am becoming desperate with tvheadend. It seems like a great way to organize my tv recordings, so far so good.
My problem is that tvheadend is unable to find muxes or services although I can guarantee the existence of tv channels on the given frequencies. The tuner itself can't be the problem either, I'm able to find channels with w_scan on the same machine.
My tuner is a Hauppauge WinTV-HVR-1975 (in my case the DVB-C functionality is needed), linux drivers are obviously loaded and working. My service provider is Unitymedia (formerly KabelBW) in Germany.
One example of a receivable tv channel ("ARD"/"Das Erste"): 362 MHz, QAM/256, 6900 KS/s (info pulled off of my tv)

When trying to add and scan a mux, the following shows up in the logs:

2015-10-03 23:09:20.000 mpegts: 362MHz in KBW - tuning on SILG DVB-T/T2/C ATSC : DVB-C #0

2015-10-03 23:09:21.126 subscription: 01B7: "scan" subscribing to mux "362MHz", weight: 2, adapter: "SILG DVB-T/T2/C ATSC : DVB-C #0", network: "KBW", service: "Raw PID Subscription" 

2015-10-03 23:09:22.382 linuxdvb: SILG DVB-T/T2/C ATSC : DVB-C #0 - poll TIMEOUT

2015-10-03 23:09:25.000 mpegts: 362MHz in KBW - scan no data, failed

2015-10-03 23:09:25.000 subscription: 01B7: "scan" unsubscribing

Before you ask, I tried this in tvheadend version 4.0.6-4 from ubuntu packages and the latest build (4.1-540) from GitHub. Both versions had the exact same problem.

Thank you guys, help is appreciated