fill bucket bug?

[guus]

I have a problem with the fill bucket tool.

I scanned in a pencil drawing, removed the white background with color to alpha, and now I'm coloring it in.

The first bucket fill works like a charm, see screenshot.     

However WHATEVER I do next, (could be creating a new layer, or using another tool, or select something....anything.) the image gets distorted afterwards. The distortions also stay when saving/restarting gimp. (see screenshot 2)     

What am I missing here... or is this a bug?

[rich2005]

You have a layer effect (fx) applied to the bottom layer.  That probably comes from the Color-to-Alpha you applied. You can merge using the FX in the layer dock (or when using Color-to-Alpha there is a "Merge filter" option ).
Delete the new top layer, merge the FX and try again.

   

However, going by past experience with scans there is a good chance that  color-to-alpha with default setting has left some very-semi-transparent artifacts.  Try increasing transparncy threshold or decreasing opacity threshold or both).
The bucket fill setting should be ok (fill similar) but it is worth trying "fill by line art detection"