Too STRONG of a signal, could have adverse effects as well.. so its possible its that... too much feedback in the one channel range (especially could happen if that frequency range is towards the inside/outside of the freqency ranges).
At my first basement apartment, the owners had a power booser in, to get good signal to their upstairs TVs.. no boxes. But we were having problems with our digital box. guy came in, and removed the power booster from our lead, and left it for the others.. and it started working fine.
I had a NextBox 3 for a few months and created a spreadsheet of signal strength readings for certain channels, including the frequency (Mhz) being used (see below). The left column is the channel and the next one is the frequency in Mhz. The data was collected over a period of several days. As you can see, the frequency for each channel moves around a lot and there is one frequency assignment of 717 for channel 552 (HBO 2).