The solution to your problem is on the Angstrom site. I won't post the solution directly here because the Angstrom team does not approve of using these forums for Angstrom assistance.
I ran into this problem last night when I flashed to 2007/4/22 unstable version.
Here is the
link. I used the first pointercal listed and it is working well for me.
Watch out for the backlight issue as well which seems to have a fix posted in the Angstrom user mailing list. The archive of the posts are
here and
here. I haven't tested these ones out yet so, caveat emptor and all that jazz.