hi,

1) RS line must be [re]set before E.
2) you said "LCD initializes correct" - how did you determine it? Could you post the initialization code here, please? It may be that you have initialized LCD to 4-bit bus mode and then use 8-bit mode.
3) if I understand right, you use timer 0 interrupt, do you? What is its time base?
4) (just a note) Always post your code with copy-paste method and use next format:

<PRE>
put
  code
      here
</PRE>

Regards,
Oleg