Did you also have to use the manual java install entry? What this error is saying is that it cannot find jarsigner in the JDK directory. This can be an error when the JDK is not properly appended to the windows path variable or the JDK is not installed.
Could you give me more information about your machine. If memory serves you run Linux so is this from within Wine?
If you are on an XP or win7 machine thing that will help me correct this for you are:
1) Did the JDK location get appended to your path variable. start>run>cmd[enter]>type: path[enter]
Check to see if the JDK is there ie: c:\Windows;c:\Windows\System32;C:\Program Files\Java\jdk1.6.0\bin
2) Is there a valid registry key for the JDK?
Start>run>regedit[enter]
The key you need to look for is: "HKey_Local_Machine" "Software" "JavaSoft" "Java Development Kit" <installed version> "JavaHome"
The JavaHome key needs to point to where your JDK is installed.

I apologize for the wall of text, but this problem with the Java in the path has been a thorn in my side for this project :| When I tried to use absolute paths when calling jarsigner it overran the input buffer :'(