I've now had the whole unit out again and blasted the selector knob unit with Air Mass electrical cleaner.

This has stoppped the erratic selections but now nothing happens when pressing the knob to make a selection.

The radio is stuck on the FM frequency band and all selections on the radio control panel are not working. Only the volume control works but the radio cannot be switched off when pressing the radio knob.

The Menu button is not working so i'm unable to get back from radio display to computer or sat nav display. Radio stations on selected FM Band can be selected on the steering wheel selector.

All these problems may be related to the computer selector knob not making correct contacs, but not sure.

Any help or technical input to this problem would be much appreciated!! Otherwise here i come Ebay!!

You most likely have a displaced dome inside the switch assembly. Pull it apart and reassemble, some glue might be necessary to keep it together afterwards.

I think that LA-Sean nailed your root cause. If you are still running an 11 year old original battery, that is likely the problem. These cars are all computer controlled. When a battery fails, failure to start is often the last symptom you will encounter. When a battery approaches end-of-life, you start to get strange, inconsistent symptoms across multiple, unrelated systems.

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SOLD
2000 E38 750iL Highline Edition, Upgraded with the lastest 2006 X5 Electronics
MKIV Navigation, 16:9 Display, Bluetooth, TV/Video with Backup Camera, Sirius, and Aux Input

Thanks for all the inputs.
Will first take the switch apart although it looks like a tricky job!!
Then if that fails, i'll look into a new battery.

Another thought, if it is the battery,wouldn't the problem go away when the engine is running as power is then coming from the generator?

Further check of system. After squirting the selector knob with electrical fluid yesterday it now seems to be working ok, can move the curser without it jumping and can make radio selections on the stuck FM freq Band. So relieved i dont have to take the selector assembly apart!!

Ckecked battery, and the Hydrometer colour is green, which indicates it doesn't need charging or replacement.

After selecting ignition switch on, control panel display temporarily shows computer menu before then changing to Radio FM band showing all pre memory radio stored channels for that band.

Unable to make any selections on radio panel, that is change functions to CD, Cassette Tape, Select Freq Bands, or turn radio off by pressing on/off Knob.The Menu button also doesn't work so cannot revert display back to computer display, very annoying as at the moment i cann't use the Sat Nav or TV.

I've checked all fuses and re checked the function of Sat Nav Map CD and loading new CD's in CD Changer in car boot.All seem to be working ok.

Cann't really think what else to do ----Any further suggestions would be welcome.

Purchase a control panel from Ebay, after installing everything is working again.

The panel control knob is a vital component since after selections are made the knob unit sends info via I-Bus to each avionic component in the car boot, then info is sent back from each unit to be displayed. Since this selector knob is used so often and can easily go wrong, i'm disgusted BMW have no means of replacing it!! Another way to get thousand of pounds from their customers!!

Regards
Peterloc

Autotronic's post 13/11/2010 was correct about the control panel selector knob.

I took it apart this afternoon and the small dome switch was misaligned. however i found it impossible to re align. There are a couple of components within the unit that have to be realigned, but that can only be done with some disconnecting of 2 soldered tags and then resoldering after the alignment.Then you've got to put the switch back together again keeping all components aligned.I didn't manage it, so would not recommend the procedure.

I now have to find a replacement Unit before i can sell it on Ebay or use the whole panel for future spares.