Thanks Sumedh,
I was able to resolve it by replacing %26apos; with '
Finally i came out of drill down charts and started working on linkedcharts which is more suitable for my requirement.
However the .net wrapper fusioncharts.dll doesn't implement setconfiguration for linkedcharts it seems.
for example using the dll i cannot set config for overlay message, specify chart type for child charts etc..
Kindly check.
Thanks,