I have no problem with that plugin (except the MVFS layer does not work for now, since dynamic views are not yet supported on windows7), provided you do have the exact tree
yourEclipse
eclipse
plugins
com.rational.clearcase.help_7.5.0.v200910221234
com.rational.clearcase.activities_7.5.0.v200910221234
com.rational.clearcase_7.5.0.v200910221234
features
com.rational.clearcase_7.5.0.v200910221234
com.ibm.rational.clearcase.ccrefresh_7.5.0.v200910221234
com.ibm.rational.clearcase.ccimport.feature_7.1.0.v200905202348--08422A2_242663
So you can start and check if you do see this configuration.
Note: I only install it on Eclipse Galileo 3.5 and Eclipse Helios 3.6Mx.