Dolphin bar doesn't work right

[DerPwny]

It gets worse in Mode 4.
I discovered that I can see and use the cursor as long as the LED on the Sensor Bar kkeps flashin but after a few seconds it vanishes and so does the cursor.
Both light are on steadily if the Wiimote is not connected, but when the Wiimote is connected the Sync LED switches off or starts blinking and switches off after a few seconds