The board was bought in the Internet, specially desighned for Arduino.
similar to this: http://cgi.ebay.co.uk/Arduino-LCD-Keypad-Shield_W0QQitemZ220513220104QQcmdZViewItemQQptZUK_ToysGames_RadioControlled_JN?hash=item33579cb608
6 digital I/O used for LCD control 1 analog input for 5 buttons.
Actually, the value of the analog pin is variable, to locate the button pressed.
When a value of parameter 1 is (for example) is 300 and the value of parameter 0 is 6, after transition from parameter 1 to parameter 0, the display shows: 600. When the "Down" button pressed again (where is nothing below zero) the display shows the correct value: 6.
I read somewhere, that it takes about 100usec for analog reading. May be a delay about 1mSec after analog reading could fix the problem?