Yes, this is possible!
First of all: the purple light underneath the rabbit that tells you your rabbit is perfectly connected: Forget about it! Once, you got the Nabaztag connected for a few seconds, you cannot rely on that light anymore! Even if you pull the router from the wallet, the rabbit will still flash purple underneath!... then the WLAN connection of your router to your nabaztag aborts at some point and then your rabbit reacts like half-dead.
First of all: Have a look at your router's manufacturer's ENGLISH website (English is most likely updated first than anything localized) whether there is a firmware update for yours.
For my Netgear WPN824v2 on the North America site (and only there!!!) there is a new firmware release from December, 16th which fixes some DHCP IP address assignment issues:
It changes the GUI of my router to English but better than having problems!
Secondly: Assure the wireless signal is good! Put your rabbit into blue mode:
/tag : http://help.nabaztag.com/fiche.php?langue=3&fiche=45
Open the configuration page in your browser (http://192.168.0.1)
Read the signal strength's. 6 or below? Too weak, re-position your router or rabbit and make it fit.
Then if the connection stands it stands and your Nabaztag / /tag will work perfectly. Once a day or so it still disconnects? Well, then the Violet server had a hickup but your rabbit will now successfully reconnect without issues!