This is no longer an issue. The following Lighning update most likely fixed it:
xul-ext-lightning (1.2+build1-0ubuntu0.11.10.1) to 1.3+build1-0ubuntu0.11.10.1
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Thanks, but if you had reported the bug using Apport, I could have told
you that without even needing to ask any questions
** Changed in: thunderbird (Ubuntu)
Status: Incomplete = Invalid
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What version of lightning are you using? Also, please use Apport to
report bugs. Please don't use the Launchpad interface, as pretty much
every piece of important information is missing from your bug report
** Changed in: thunderbird (Ubuntu)
Status: New = Incomplete
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