hatuan291,

What PIC are you using? The DS1820 has its limits in speed as stated in the datasheet. First try using a PAUSEUS after the conversion command.

Code:
OWOut DQ, 1, [$CC, $44] ' Start temperature conversion
Double check that your PIC is working with the new oscillator settings. Try a blinking LED first with the new settings.

http://datasheets.maxim-ic.com/en/ds/DS18S20.pdf

Robert