If security center service is missing or damaged, or antivirus software is not installed and current, Outlook 2010 will not allow sync with other apps without prompt. Eg. Commit.
You could try adding the following key to the registry:
In this key add the following value:
ObjectModelGuard, DWORD =2
The values 0, 1 and 2 correspond to the options in the Programmatic Access Security settings in the Trust Center.
0 = Warn if Anti-Virus is out of date (recommended)
1 = Always warn
2 = Never warn