If you have removed WebTop 4 from Software Center and after that you have installed WebTop 5 from Software Center, could be some things which has remain from WebTop 4, that are incompatible with WebTop 5.
Could you try the following procedure?
# yum remove nethserver-webtop5 webtop5-core webtop5-libs webtop5-zpush
# rm -rf /var/lib/tomcats/webtop
# yum remove nethserver-webtop4 webtop4-core webtop4-libs webtop4-zpush
# rm -rf /var/lib/tomcats/webtop (just to be sure)
# yum install nethserver-webtop5 (or install it from Software Center)