I had the same issues when I updated to 1.76 from extras-devel. Check if your is the same version (open transmission, tap the top bar where the title is and click 'about'). If thats the case, uninstall it, then disable extras-devel and install version 1.75 from extras. This one does not reboot my n900 anymore, it doesnt make anything read only and it seems to lag a little less.