Alienoide, I have a DCS-5222L as well and had issues with it dropping the wifi connection, ended up being a poor internet signal on Mediacomm's cable ..i added a Channel MAster Distribution amplifier to boost the signal and that helped dramatically. But I have a question; have you tried scheduling a reboot in the camera settings , maybe once a week ? theory being that a scheduled therapeutic reboot would cause the camera to rejoin the wifi, I have considered this, but have not tried it yet...no faith in Dlink's software !
JR