* Al Qaeda videographer was serving life term at Guantanamo * Court: Conspiracy, other counts weren't war crimes in 2001 * Ruling casts doubts on other Guantanamo convictions (Adds quotes, details) By Jane Sutton MIAMI, Jan 25 (Reuters) - A U.S. appeals court on Friday overturned the Guantanamo war crimes conviction of an al Qaeda videographer, a ruling likely to lead to dismissal of conspiracy charges in the pending trial of five men accused of plotting the Sept. 11 attacks.