problem with cyclone III and jtag

Page 9-49 of the Cyclone III datasheet:

http://www.altera.com/literature/hb/cyc3/cyc3_ciii51016.pdf

reads:

--- Quote Start ---

For device VCCIO of 2.5, 3.0, and 3.3 V, refer to Figure 9–24. All I/O inputs must

maintain a maximum AC voltage of 4.1 V. Because JTAG pins do not have the internal

PCI clamping diodes to prevent voltage overshoot when using VCCIO of 2.5, 3.0, and

3.3 V, you must power up the VCC of the download cable with a 2.5-V supply from

VCCA.

--- Quote End ---

It is unfortunate that this was overlooked. You say the boards had been working and have failed. It is possible that the FPGA has been damaged.

Jake