Hi All,
I thank all of you for helping me in solving this problem…
Actually by just using the snubbers across the motors solved the problem…

Though the problem was solved by just using the snubbers we also used a VDR across the main transformer , a 7.4v zener across the main 5v power supply,a 100pF capacitor across the 10uF capacitor close to the uC. And above all this the boards were assembled inside a mild-steel panel.

We were not able to find ferrite beads, we are trying to source them.

All in all it was a good lesson we learnt …

I have collected a 5 page precautionary measures from the previous postings and will implement it in the future designs. Thanx to all those people who have shared their practical experience…and a special thanx goes to Steve for managing such a beautiful forum…

Rgds
Raj Shetgar