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Not sure if IE plays well with thunderbird,try it with FIREFOX
Also check this LINK
Try scanning with your AV and AVG ANTI SPYWARE in safe mode.
On opening some attachments, they open for 2/3mins,then black screen for 2/3secs,then blue screen containing data, 2/3secs. Pause has no effect,so can't read data.Computer then restarts itself.XP Pro SP2,1G ram, NAV,Win Def, Spybot etc Any reasons and cures?G