I've seen this with long loginnames, depending on which version of the
database you created your setup with. In my case, Emerald will allow up to
16 characters for a login name, but the calls table will only hold 12, so
when a call is attempted to be inserted into the calls table with a name
longer than 12 characters, it is rejected as having too long a name. The
user never appears online in any report, but signs on/off without difficulty.
My database was created some time back and will be re-created when we get
the next database fix (I figured I'd wait for 2.2 and all it's changes to
dump and reload), and more recent versions of the SQL to create the
database have increased the value to 32 characters, so this may not be your
problem, but I thought I'd mention it just in case.