I’ve been seeing a number of reports on an error while synchronizing with ACT, with an error message indicating something along the lines of:

String was not recognized as a valid DateTime

The errors have thus far come from Germany and The Netherlands. The team has already investigated the issue – it is, indeed, a globalization bug. They have a fix in place for ACT 6.0, but for now to work around the problem you will need to change the Windows locale to English-US. Sorry for the inconvenience, but wanted to unblock those who were confused by this by sharing the workaround.