We have found that the DViCo Dual Digital 4 Tuner card is not completely stable under the 07.10 Kernel and v4l-dvb drivers. See http://www.linuxtv.org/wiki/index.php/DViCO_FusionHDTV_DVB-T_Dual_Express. The tuners seem to disappear fairly frequently and then a reboot is needed to get them back again.
Whats the stability like for you?
I understand that the situation might be much better under 08.10's 2.6.27 Kernel though.
Yes you can upgrade the Kernel used under LinuxMCE 7.10.... but I would not recommend it until you are more familiar with the system...as you can easily trash your system.
In your case you should see an 'adapter2' as you have three DVB tuners. If you only see 'adapter0' then that would explain why MythTV wants to end the 'in-progress' recording when you request a channel change or to start another recording. If you do have only 'adapter0' then only one of your tuners is recognised and their is something wrong with the kernel modules you have loaded currently.