[Antagonist]

I am not sure if this is related...

I am the exchange admin at my company. I started seeing the same symptoms you describe. I temporarily switched off "forms based authentication" on the exchange server...problems went away. I switched it back on...guess what...problems STAYED gone. I did notice the same behaviour in my logs...sometimes the phone would send authentication information...sometimes it wouldn't. After doing this...it didn't matter. Sync works perfectly all day and I have flashed the phone with several (okay 11) different builds and it still syncs perfectly after each. I am currently running the official release (for about a week) and it has not dropped sync once. Hope this helps someone. Just my 2 cents.

For me at least, it seems the phone couldn't reliably deal with the forms login (if using OWA, it's the screen that looks like a starndad outlook login...if forms is turned off, you see a standard username and password prompt instead of the graphical login.)