Latest plesk version is 9 which is nothing but mess, its better to write to support of plesk ( you will get canned messages mostly) sometimes if you have luck you will get solution
The issue got resolved long ago, I installed plesk_8.6.0 version and it started working pretty fine.May be the problem was that the package I was installing at that time was full of bugs or corrupted.I have downloaded a new package and it got installed and unistalled properly.