Macbook Pro/iTunes not detecting iPhone4

I know this question has been asked many times and I did searched and tried solutions available but still in vain.

- iPhone is charged by the usb cable.

- the iPhone was detected months ago (for the last backup).

- OS X and iTunes are most updated.

- doesn't appear in image capture or iPhoto

- tried force restore of iPhone4 but didnt' work (still didn't show up in iTunes)

I tried:

http://support.apple.com/kb/HT1747

- I can't drag the iTunes icon to trash because it is required by OS X. I did trashed the content folder.

http://support.apple.com/kb/TS1591

- this still doesn't work for me

Does anyone know what to do? Thanks for your help!