Shift Ident Right/Left Deletes Text

Shift Ident Right or Left (Alt-Right/-Left), when used
with more than just a few lines selected, often causes
that the selected text is removed and one single
character is inserted instead.(often a "B").

When this happens, I press Ctrl-Z (undo). This
reinserts the text with the new identation.

This problem exists since a long time and is still
there in 4pre7. It is also not JRE specific since a
have updated my JDK several times since the first
occurence.

Manfred