so usually java.exe should be the right one.
could you try to open a command window (type "cmd" in the start menu)
and post the outcome of
java -version
and then (from the directory where the visone-2.6.5.jar resides) the
output of
java -jar visone-2.6.5.jar
since it also does not work with older versions it is likely to be a
problem with your java runtime environment.
Besides that, does the webstart work for you?
Uwe