Add group or user name..Bug or not?

Hi.. I just want to know if anybody else has experienced this problem.
When i try to add group [xx\yyyYYYY Datakontakter] to a role on a folder the
response is "The user or group name 'xxYYYY Datakontakter' is not recognized.
(rsUnknownUserName) ". However, when it is [xx\xxxYYYY Filialchefer] it is
ok.
The difference are that the first one have 21 characters after the \ and the
second one 21. To make it even more interesting if i try to add the second
one with its [pre-2000] name, which is [xxxYYYY Region-1] it is ok. Now, i
havent yet tested if it really works after adding the group, so i´m not in
the clear yet. Anybody else experienced the same problem?It should be:
The difference are that the first one have 21 characters and the second one
20. To make it even more interesting if i try to add the FIRST one with its
[pre-2000] name, which is [xxxYYYY Region-1] it is ok.