I have a Canon 6D. The "File Numbering" setting is set to "Continuous", and for the most part, it behaves that way. However, unlike my experience with previous Canon DSLRs (e.g. my Canon 30D), ...
Canon use only 4 digits in the filename (eg: IMG_1234.jpg) My camera has wrapped around the file numbering so that I now have 2 photos on the memory card with the same name. Picasa fails to import ...