Certain PowerPC chips have escalation counters. These counters will keep track of consecutive resets and, if there are too many in a short period of time, the chip goes into a permanent reset. As a result, winIDEA cannot establish a debug session since the chip is in reset.
The solution is to reset the escalation counters to their initial values, which can be done with an initialization file. This is an example of an initialization file that resets the FRET and DRET registers on MPC5746C:
A 0xF7FA8604 L 0x0 // Reset RGM_FRET
A 0xF7FA8608 L 0x0 // Reset RGM_DRET