Log4j reports the following:
[GDS_Impl,INFO] Attempting to loadLibrary for "jaybird"
[GDS_Impl,INFO] loadLibrary for "java_gds" returned OK.
[GDS_Impl,INFO] Attempting to initilize native library.
[GDS_Impl,INFO] Failed to load client library # 0 - "fbclient.dll".
[GDS_Impl,INFO] Initilized native library OK.
[GDS_Impl,DEBUG] Original file name: e:/db_dh.gdb
[GDS_Impl,DEBUG] File name for native code: /db_dh.gdb
[FBManagedConnection,DEBUG] Could not get a db connection!
org.firebirdsql.gds.GDSException: I/O error during "CreateFile (open)"
operation for file "D:\DB_DH.GDB"
Error while trying to open file
null
at org.firebirdsql.ngds.GDS_Impl.native_isc_attach_database(Native Method)
at org.firebirdsql.ngds.GDS_Impl.isc_attach_database(GDS_Impl.java:235)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at
org.firebirdsql.gds.GDSSynchronizationPolicy$AbstractSynchronizationPolicy.i
nvoke(GDSSynchronizationPolicy.java:100)
at $Proxy0.isc_attach_database(Unknown Source)
at
org.firebirdsql.jca.FBManagedConnectionFactory.createDbHandle(FBManagedConne
ctionFactory.java:540)
at
org.firebirdsql.jca.FBManagedConnection.<init>(FBManagedConnection.java:88)
at
org.firebirdsql.jca.FBManagedConnectionFactory.createManagedConnection(FBMan
agedConnectionFactory.java:366)
at
org.firebirdsql.pool.FBConnectionPoolDataSource.allocateConnection(FBConnect
ionPoolDataSource.java:146)
at
org.firebirdsql.pool.PooledConnectionQueue.addConnection(PooledConnectionQue
ue.java:403)
at
org.firebirdsql.pool.PooledConnectionQueue.start(PooledConnectionQueue.java:
156)
at
org.firebirdsql.pool.AbstractConnectionPool.getQueue(AbstractConnectionPool.
java:182)
at
org.firebirdsql.pool.FBConnectionPoolDataSource.getFreeSize(FBConnectionPool
DataSource.java:314)
at
org.firebirdsql.pool.FBWrappingDataSource.getConnectionCount(FBWrappingDataS
ource.java:353)
at
com.TTC_Informatik.PAULA.server.App_Server.getConnection(App_Server.java:939
0)
at
com.TTC_Informatik.PAULA.server.App_Server.getReadConnection(App_Server.java
:7554)
at
com.TTC_Informatik.PAULA.server.App_Server.getAllDBObjekte(App_Server.java:2
618)
at
com.TTC_Informatik.PAULA.server.App_Server$7.construct(App_Server.java:7827)
at com.TTC_Informatik.PAULA.Tools.SwingWorker$2.run(SwingWorker.java:109)
at java.lang.Thread.run(Unknown Source)

fbclient.dll is in system32 dir.
I tested it with fbclient.dll in my working dir with the same error.

mfg
Carsten