Same here running Ubuntu 10.04 64 bits ( Linux user-desktop 2.6.32-24-generic #39-Ubuntu SMP Wed Jul 28 05:14:15 UTC 2010 x86_64 GNU/Linux )

java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.Integer
	at utils.GtkStockIconSWT.createImage(GtkStockIconSWT.java:120)
	at utils.StockIcon.getGTKImageData(StockIcon.java:275)
	at utils.StockIcon.getIcon(StockIcon.java:161)
	at core.MainWindow.createSShell(MainWindow.java:227)
	at core.MainWindow.<init>(MainWindow.java:200)
	at core.Loader$Worker$3.run(Loader.java:495)
	at org.eclipse.swt.widgets.RunnableLock.run(Unknown Source)
	at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Unknown Source)
	at org.eclipse.swt.widgets.Display.runAsyncMessages(Unknown Source)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
	at core.Loader.main(Loader.java:235)
Exception in thread "main" org.eclipse.swt.SWTException: Failed to execute runnable (java.lang.IllegalArgumentException: Argument not valid)
	at org.eclipse.swt.SWT.error(Unknown Source)
	at org.eclipse.swt.SWT.error(Unknown Source)
	at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Unknown Source)
	at org.eclipse.swt.widgets.Display.runAsyncMessages(Unknown Source)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
	at core.Loader.main(Loader.java:235)
Caused by: java.lang.IllegalArgumentException: Argument not valid
	at org.eclipse.swt.SWT.error(Unknown Source)
	at org.eclipse.swt.SWT.error(Unknown Source)
	at org.eclipse.swt.SWT.error(Unknown Source)
	at org.eclipse.swt.graphics.ImageData.<init>(Unknown Source)
	at org.eclipse.swt.graphics.ImageData.<init>(Unknown Source)
	at utils.GtkStockIconSWT.createImage(GtkStockIconSWT.java:155)
	at utils.StockIcon.getGTKImageData(StockIcon.java:275)
	at utils.StockIcon.getIcon(StockIcon.java:161)
	at core.MainWindow.createSShell(MainWindow.java:227)
	at core.MainWindow.<init>(MainWindow.java:200)
	at core.Loader$Worker$3.run(Loader.java:495)
	at org.eclipse.swt.widgets.RunnableLock.run(Unknown Source)
	... 4 more

Here info about my java installation:

dpkg -l *java* | grep ii
ii  ca-certificates-java                  20100406ubuntu1                                 Common CA certificates (JKS keystore)
ii  java-common                           0.34                                            Base of all Java packages
ii  libaccess-bridge-java                 1.26.2-3                                        Java Access Bridge for GNOME
ii  libaccess-bridge-java-jni             1.26.2-3                                        Java Access Bridge for GNOME (jni bindings)
ii  tzdata-java                           2010k-0ubuntu0.10.04                            time zone and daylight-saving time data for

dpkg -l *jdk* | grep ii
ii  openjdk-6-jre                         6b18-1.8-4ubuntu3                               OpenJDK Java runtime, using Hotspot JIT
ii  openjdk-6-jre-headless                6b18-1.8-4ubuntu3                               OpenJDK Java runtime, using Hotspot JIT (hea
ii  openjdk-6-jre-lib                     6b18-1.8-4ubuntu3                               OpenJDK Java runtime (architecture independe


Thank your for reviewing this, I like this program.