Guessing (although not much guessing to do with the info you gave
) that you installed via Fantastico and therefore, the version has nothing to do with your ISP unfortunately (ISPs have no control over Fantastico).
The good news is 1.6.1 should be included in Fantastico soon
The bad news is, IMHO you really shouldn't use Fantastico for any script other than to have a quick look really. As you have seen, using Fantastico there is no real control over the version of scripts, therefore, you have no control over upgrades which is a concern, especially if security related.
If I was you I would have a look into installing Moodle yourself (preferably via CVS if you can for ease of upkeep). It is really not that difficult to get your head around (I did my first install with no background knowledge really within about 30 minutes) and gives you much more control over things.
Regards
Harry