I am having the same problem. I also posted a question regarding this problem yesterday in the forum but up until now I have received any answers. I also send an email to HTC support but haven't heard from them yet. I suggest you do the same, this way they can't say that this is a one time problem ;)
I was about to do a factory reset, but now I am afraid that this isn't going to solve my problem. My phone has been working without any problems for 2 weeks with a lot of facebook people synchronised to my contacts. I think that 1of the facebook contacts has some illegal character is its name or description and thus giving this error.
Spoke to soon. This is the reply from HTC. But it isn't that helpfull I am afraid ;-(
Dear HTC customer,
Thank you for contacting our Customer Support Center. We are dedicated to providing you with the best quality service and answering all of your questions and concerns.
Thank you for your feedback, please try to do a hard reset of your phone to see if that solves the problem. You can do this by:
1. With the phone turned off, press and hold the HOME and BACK buttons, and then briefly press the END CALL/POWER button. The reset process will start after a few seconds.
2. Wait for the phone to finish the reset process and then press MENU.
If this does not solve the problem there should be a ROM update for the Hero coming out soon which could contain a fix for the problem. Try the hard reset if it doesn’t work keep an eye on htc.com for the ROM upgrade for the Hero.
If the above steps do not resolve your issue, we invite you to visit the support area on our Web site. Please go to: http://www.htc.com/www/support.aspx
Or you can go to: http://www.htc.com/select_country.htm
, select your country and then click on the Support tab.
You can also call our Call Center at: +46-85-055-6438 if you have further questions.
Thank you once again for your continued patronage.
Europe customer support team
HTC Corp. Global Service Division