I do have access to a parallel programmer. Now what exactly should i do to get the chip back to the "ISP" mode?
When you select the P89C51Rx2 or P89C51Rx2H they program different, make sure you pick the right one, you will find that there is a window for the boot vector, set that to the right value (see datasheet/AN461). The status byte is handled by the "funny levels" at reset.

Erik