> Is the JDBC driver open source?

Source is available for download from SourceForge.net:

http://prdownloads.sourceforge.net/firebird/FirebirdSQL-1.5.1-src.zip?download

and

http://prdownloads.sourceforge.net/firebird/FirebirdSQL-1.5.2-src.zip?download

> If it is - and before I look at any code - can you tell me is there any
> code that is dependant on the version of the operating system?

No.

> I.e if (win2000) do this or that? Are there any special exceptions
> (on a per-OS basis) for handling files, processes, threads,
> security, etc?

No.

Most likely this is system-dependend behavior of the JVM in the
"synchronized" section. Or a bug in a driver that happens on W2k.

Roman