1) Can you be sure the kernel includes a fix for the database leak in com.noshufou.android.su - this is definitely an issue in bb 0.4
some more detail on this: at
Issue 1512 - cyanogenmod - Superuser database leak - Project Hosting on Google Code
2) Also, could you ensure the kernel included with bb has requisite netfilter options for wireless tether?
more information on this at
Issue 427 - android-wifi-tether - Issues connecting use Droid (BuglessBeast 0.4 Froyo) - Project Hosting on Google Code
bb included kernel was configured and compiled without all of the necessary netfilter options.
Need to make sure that the kernel configuration includes both CONFIG_NETFILTER_XT_MATCH_MAC=y