Help burning bootloader to atmega 2560

Hi folks,

I am in a bit of a situation here:

I have a modified arduino mega board that is embedded in one of my projects.

Due to a fault on an AC adapter (isolation) on one of the slave boards the SDA pin got blown.

Anyway, I took the IC off and soldered a new one. All straight forward.

Now burning the bootloader, the chip sometimes works sometimes not. After uploading code a few times it just dies and I have to upload the bootloader again. Sometimes it does not see the serial port. Doing all sorts of strange things.

Hardware wise everything nice and clean. I am using a USBASP