I recently had the problem with a HTC Desire where a Google account was added but only mail and contacts could be selected for synchronization, there was not abvious way to fix it and none of the clear your google account didnt work for me. The alternative to clearing the Google account was to do a factory defaults on the phone which wasn’t an option.
So the solution was to create and add a second Google account. As soon as it was added the first account fixed it self – the calender suddenly appeared. Then I could just delete and remove the second newly created account from the phone again.
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