Had an instance of mysterious "permissions error" when logging in to a 6.1 Mac server. Every time. Permissions were all correct.
After some investigation, the problem turned out to be that the server had an incorrect DNS entry. Since MoneyWorks Datacentre needs to open network connections to itself as part of the login process, it is necessary for any DNS entry for the server to be correct. Evidently, earlier versions did not mind incorrect DNS but 6.1 does (possibly due to the changeover to BSD Sockets from the deprecated Open Transport API).
If you are seeing this error, and you know that permissions are correct (have run Console to set documents folder ownership to moneyworks_server), then please check the DNS.
If the server has a DNS name (e.g. accounts.company.com), open terminal on the server and try:
The IP address from host should be the same as the inet address for interface (typically) en0.
If the server is behind a NAT device and has DNS for its external IP address, then ensure that there is a hosts file entry so that local hostname lookups resolve to the internal IP address.