As an Xtreme DSP Kit user, I sometimes reach the limit of the +1.5V core linear voltage regulator used on the power modules incorporated into the Xtreme DSP Kit mother board.
In demanding applications, the XC2V2000 and XC2V3000 parts may require more current than the maximum that can be supplied by the FPS (Fixed Power Supply) power module. In high utilization or high frequency designs, you may see the +1.5V FPS fold back or shut itself off due to the thermal limits of the device. When the FPS shuts off, the FPGA configuration is eliminated.
You need to replace the FPS with a Programmable Power Supply (PPS). For further technical details on this problem, please consult the following application note: