no iTunes? this is crazy :-)
For me no solution cause I got an iPhone

But what did the trick for me was ...finally... to "idlehalt=0"

Since then I have pretty stable system, no Thunderbird problems,
Systems running now for 2 Days without any problems or mouse bugs

Lawless 10.5.4 / Stage XNU / Disabed QnC / and Idlehalt=0