Screen corruption & possible crash (*solved*)

[LCD]

LCD, I have discovered that, removing line

Code:

s$ = ""

makes the program to run ok. :?: So this could be an easy bug to fix.
Meanwhile, can you check your program removing this line?

I added this line only for testing. It still happen, but after a longer time, even longer if I remove DIM s$ as String.
This is the actual version of Clock Function:

Code:

function Clock(tim as uinteger) as String dim mins,sec as ubyte dim secs as uinteger secs=int(tim/50) mins=int(secs/60) sec=secs mod 60 m$=str(mins) if len(m$)=1 then m$="0"+m$ end if s$=str(sec) if len(s$)=1 then s$="0"+s$ end if return m$+":"+s$ return str(int(tim/50))+" " end function

Still causing a crash. After Meeting in Wittenberg this weekend, I can mail you the complete source code. After one minute (or less) of playing, the game locks up.
Sorry it it is not that easy.