Bruce, I just re-read your post and see that you already
have pull-downs. Hmmmm.......

> Then I call this code to read the switches on portb(4..7):
> 
> setb    rp0
> mov    trisb,#11110000b
> clrb    rp0

Have you tried a delay here ? Could be some residual
charge or capacitance

> mov    Temp_lvl,portb
> swap   Temp_lvl
> and    Temp_lvl,#00001111b

BTW, Maarten, the Parallax code in PIC terms is

movf  portb,w  ;copy portb to Temp_lvl
movwf  Temp_lvl
swapf  Temp_lvl  ;switch values into LSN
movlw  b'00001111'  ;test for '1's
andwf  Temp_lvl

Are internal pull-ups on ? I think nominally they are around
27k, which might marginally balance the 20k pull-downs

If they are off, the problem must be elsewhere (duh). Either
the port isn't being set up correctly (perhaps a peripheral is
enabled ?) or for some external reason the pins really do
always have '1' on them. Have you looked at them with a
'scope or meter ?

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