Wireless Mouse problems

I finally took delivery of a RasPi today, and along with it came a Xenta wireless keyboard and mouse.(Bought from ModMyPi)
The os is Raspbian and the keyboard is working well, but the mouse refuses to work properly with the pointer continually rushing to the bottom of the screen and refusing to work above the panel without a real struggle. Tried a wired usb mouse and that is perfect, and the RasPi working as expected for the first foray into this realm.
Question is has anyone else encountered this problem, and if so were they able to fix it and get it working.
Any pointers and help gratefully accepted as I am a complete newbie with linux,
Thanks.

Its not this model is it, because it is listed on the wiki as having problems with the pi?

Multimedia Wireless Keyboard and Mouse Set (Keyboard Model: HK3518B + Mouse Model HM3301) (B) - occasional sticky keys, and occasional complete lock-up

No, it's not that model, though it may be a power supply issue, I am using a Blackberry charger to power the pi, although everything else seems ok, but this is only day 2 for me, so I'll not worry just yet.

Well, problem solved (thanks to Jacob Marsh at ModMyPi.com) he suggested testing the voltage and it was borderline at 4.8v, so I switched to a HTC phone charger from the Blackberry and now the wireless mouse works perfectly.The HTC is giving 4.95v.
Now I can hide the Pi behind the tv now, happy days.

Same problem has returned! I have a hell of a lot to learn

Well, update is I managed to completetly crash my Raspbian Wheezy OS so this morning I learned how to re-flash a sd card and then re-partition the new card and get everything up and running again, (I am typing this from my Pi). It actually pays to make mistakes with the Pi, so I guess, in my case, this device is already teaching me new stuff, which is it's fundamental aim.
Learning basic computing at 50 is a steep learning curve for a life long manual worker with no previous experience, but cold sweats and panics aside, it's enjoyable stuff. Now i will start to actually learn stuff, I hope.

Well, the mouse problem is back, and seems like it's here to stay, nothing seems to help it, I have re-imaged the sd card but to no avail. So any new suggestions will be welcome.
Sorry for bumping this post again.

Same problem here, even when using decent power supply and good batteries. Will contact modmypi about a refund