I am having some serious issues here all of a sudden.
One computer running vin7 with Dragon and a ATmega2560 can program and verify fine, but is unable to debug. (Hangs after run/reset and never reaches start of main.) A quick test of reading memory gives random 0x00's or 0x01 etc. Comms between programmer and target is fine as it can program and verify.
Machine was running 4.18 and it was upgraded to SP3 with no solution.
Another pc running xp was tested with ICE MKII and a ATmega128 using 4.17 and it has the same issues! I also tried the Dragon on it with no change. Upgrading to 4.18 SP3 made no difference.
I tried verifying target vs actual IC and they match.
This is all very strange and any suggestions are welcome.