“Dear Xiao-Fan and Min,

Greetings from Beijing! I had wanted to attend the 2009 CBIS conference in San Diego but had to cancel my flight reservation due to a tough personal
situation.”

comment:no serious errors, but I would like to change it as follows:
"Greetings from Beijing! I had planned to attend the 2009 CBIS conference in San Diego, but had to cancel my flight reservation due to tough personal issues."
既然已经订了机票，那就不是“想要”与否的问题，而是已经计划了而且部分实施了。所以应该是"planned".

“Although this email is addressed to the two of you, please feel free to share the content with attendees of the 2009 CBIS conference.”
评: 上文已经说了“2009 CBIS conference”，这里又重复一遍显然多余，直接说“the Conference”就够了。

“I am writing to congratulate the CBIS conference, to update my situation in Beijing, to ask for reinforcement, and to thank my friends and colleagues for your generous support!”
评："update my situation" means what? can anybody's situation be updated like a software? The correct statement should be "to update you on my situation in Beijing".
BTW: CBIS has appeared three times so far, can not you just save some typing by removing it?

“First, my warmest congratulations to the CBIS conference!”
comment: Oh, my goodness! "CBIS" again! Give me a break, please!!

"CBIS, formerly known as the Ray Wu Society..."
comment: I cannot read anymore. This guy is addicted to "CBIS" already.