I also have this problem with a recent Packard Bell netbook (made by Acer). I saw the idea post #10 to disable the touchpad using Fn F1, but it doesn't work for me- all I get is Help. However it looks like this feature is hardware based, so it depends on your laptop. On mine I just noticed that the touchpad disable feature is in fact on the Fn-F7 key. Just tried it and while posting this is the first time I ever didn't have the jumping cursor problem!
It would be nice for the feature to be automatic but this is nearly as good.
If you are having trouble, have a careful look at the Fn keys or manual to see which is the correct one. I also know that some laptops have a specific button for this.