problem fixing hold violations in cadence encounter.

Hi,

I am trying to place and route a synthesised netlist in cadence
encounter.I did a timing analysis on my trial routed block before CTS
was done.I had 2 minor hold violations when i did the timing analysis
with an ideal clock.Then after clock tree synthesis and nano route was
over I did a timing analysis.There were more than 50 violated paths
with 2 paths having huge clock gating hold violations.So I tried doing
a
hold time slack optimisation by giving a slack of 0.2 ns in the post
route mode.Before starting the optimistation I guess the tool itself
does a hold time slack analysis and it shows me that there are only 2
paths violated with very little negative slack(as against the 50
violated paths during timing analysis).The report generated after
optimisation says that there are 0 violating paths and the worst case
slack is 0.174ns.But when i do a timing analysis on the generated
layout after fresh RC extraction and delay calculation there are
still more than 50 violated paths.Can anyone please tell me why this
discrepancy is happening? Which report am i to trust?

thanks,
Nagaraj