DVB-T tuners "in error" in frontend

[Julius22]

Hello!
I didn't use my two Mythboxes for a while.
I restarted them yesterday. My main machine (master backend with a frontend) seems to work fine (except that I need to reconfigure mythfilldatabase).
But if I write my message in this section of the forum, it is because I'm facing a problem with my secondary machine (slave backend with a frontend). I want to use it in order to record TV programs with two DVB-T cards (one WinTV Nova-T and one WinTV HVR-1300)
I moved in a new area since last time I used it. So, I made a new channel search with each card. Quite no problem with this: the channels I want to use were found. But with the frontend, in the menu of the tuners state, I see that all virtual tuners of the physical cards I want to use are "in error" (I don't know if this is the way it is written in english as I use MythTV in another language).
I use MythTV on this computer with the 0.27 version and with Debian and a 3.2.0 Linux kernel.
I would appreciate any help about how to solve my problem.
Don't hesitate to ask any question if necessary.