Picasa did not show videos takes with my Panasonic LX5. I found that there is actually a simple solution — you just need to install the right codec. I installed the K-Lite codec pack, available here:
Quote: “The K-Lite Codec Pack is a collection of DirectShow filters, VFW/ACM codecs, and tools. Codecs and DirectShow filters are needed for encoding and decoding audio and video formats. The K-Lite Codec Pack is designed as a user-friendly solution for playing all your audio and movie files. With the K-Lite Codec Pack you should be able to play all the popular audio and video formats and even several less common formats.”
Now the AVCHD (.MTS) files from my LX5 appear and play perfectly in Picasa 3. And I can upload them to Picasaweb, too.