Strange Marlin issue

Hi all! I have a very strange issue on a Mendel I'm building and wondered if anybody had seen this before.

I was playing with Marlin settings to centre the print on the bed (it's a triple head version using a Melzi controller) and all of a sudden it started to heat the hot end as soon as the PC host software connects to the printer over USB. When the printer is powered up and idle, it doesn't heat the T0 tool, but when I connect using USB with either Repetier Host or Simplify3d the software connects, I see the connect string and the hot end immediately heats to 214c. All controls are unresponsive until it reaches temperature and then things go to normal, and I can switch off the hot end.

Now, the above is strange, but if I use Pronterface as the host, it doesn't do it....

I'm stumped!

Any suggestions?

OK, I fixed this issue - seems that there was a rogue setting in the EEPROM:

Extruder: 0 dX: 0.00 dY: 0.00 dZ: 0.00 standby temp: 0.00 operating temp: 215.00

I'm not quite sure how it got there, but a simple M502 cleared it and fixed the issue and the M501 now reports:

Extruder: 0 dX: 0.00 dY: 0.00 dZ: 0.00 standby temp: 0.00 operating temp: 0.00

Now when connecting with host software over USB, I get a normal connection and monitoring state, and the controls, including heaters respond as expected.

I'm really not sure how this got changed as the only command I was changing was M206 for the extruder position offsets. Hey ho!

good catch this, seen this issue raised a few times in the general section, with no answer thanks for sharing SS.