I am using ubuntu Linux 10.04 Pc in that my **Samsung Galaxy 7"** (GT-P6210) **homeycomb 3.2** is not detecting for development its showing in eclipse as

 `DeviceMonitor] Failed to start monitoring ????????????`  in **console** 

and in **device tab** its showing ?????????????.

Except this **7' GT-P6210** Samsung tablet all other Samsung devices are showing fine.

When I switch off the tablet and connected to the USB its showing the number and online as status. 
List of devices attached 
4641199B0F8488AE	device

why? whats the problem any solution.

**NOTE:**
I already Added 51-android.rules 

    Samsung	04E8 

and also I enabled the **USB debugging** mode.

Its working fine in **Mac**.