I run Ubuntu 13.04 with up-to-date Firefox and Oracle Java 7 is installed from the package oracle-java7-installer from the ppa:webupd8team/java PPA.

Java doesn't work in Firefox.

When I start firefox from the command line, and open a webpage with some java, the java applet doesn't work and in the terminal firefox prints:

$ firefox

(process:28565): GLib-CRITICAL **: g_slice_set_config: assertion `sys_page_size == 0' failed
java.io.IOException: Cannot run program "/usr/lib/jvm/java-7-oracle/jre/bin/java": error=13, Permission denied
    at java.lang.ProcessBuilder.start(ProcessBuilder.java:1041)
    at sun.plugin2.jvm.JVMLauncher.start(Unknown Source)
    at sun.plugin2.main.server.JVMInstance.startImpl(Unknown Source)
(and some 20-30 lines more)

(I guess the GLib-line can be ignored here.)

Also, when I close the tab that contained the java applet, firefox freezes and I have to kill it.

However, the permissions look fine:

$ ls -l /usr/lib/jvm/java-7-oracle/jre/bin/java
-rwxr-xr-x 1 root root 5746 Jul 22 17:35 /usr/lib/jvm/java-7-oracle/jre/bin/java

So, what could be wrong here? What to check next?

EDIT: Oracle Java is needed for stupid Danske Bank online banking. (You are of course welcome to suggest me to change my bank.)