I wanted to comment in this thread, but it's locked, so I thought I'd follow up here.

First, thanks to nosomoho for posting in that thread. I was also getting ActiveSync error 80070490 synchronizing my Calendar, and hadn't found an answer at Microsoft or Pocket PC FAQ. I did an Outlook Detect & Repair and a ScanPST, but neither worked. I did a Google and found that thread (#1!) and the solution fixed my problem.

However, here are some more recent details. I'm using an iPAQ 2795 (which was not a 2755 upgraded to WM 5) and ActiveSync 4.2. So the problem is still around.

Also, HP's manual defines three types of resets:

• The soft reset -- Pushing the stylus in the reset hole.
  
• The hard reset -- Pushing the Calendar and iTask buttons while pushing the stylus in the reset hole. This does not erase any programs or settings. HP says it's like a soft reset that also "resets all hardware registers" (whatever that means).
  
• The clean reset -- Pushing the Calendar, Messaging and Power buttons while pushing the stylus in the reset hole. This does erase any programs or settings, similar to what we called a "hard reset" back in the pre-WM 5 days.
  

I had tried a soft reset, but didn't try a hard or clean reset. As I didn't have much data on my 2795, I did a clean reset and that allowed me to sync my Calendar.

So thanks, Henny.

Steve