Your file associations have been changed by WinRAR. Re-associate .jar files with the java program, and it will work correctly.

Go to Windows Explorer, then click on Tools -> Folder Options. Then click on the File Types tab. After that, scroll to the file type JAR, and click Advanced. Click on the "open" action, then click Edit. Under Application used to perform action:, put this line in:

javaw.exe -jar "%1"

When you installed a Java Runtime Environment, this was the default setting, but you must have installed WinRAR afterwards (or let WinRAR modify your file settings). Alternately, you could re-install your JRE, run PalantirPDB from a command line, or write a batch file that would run PalantirPDB using javaw.exe -jar.