plug-in could not be found (access virus & c6)

HI!!! Once I worked with cubase 5 on windows xp, now I work with cubase 6 on mac, the problem is the following: when I open the c5 projects on c6 all plug ins work fine except virus ti that makes no sound and tell me missing vst plug ins. infact virus control doesn’t open.
I saw on the user manual this:

“ When you open a project that uses an external effect/in- strument, you may get a “plug-in could not be found” mes- sage. This will happen when you remove an external device from the VST Connections window although it is used in a saved project, or when transferring a project to another computer on which the external device is not de- fined. You may also see this message when opening a project created with an earlier version of Cubase.
In the VST Connections window, the broken connection to the external device is indicated by an icon in the Bus Name column.
To reestablish the broken connection to the external de- vice, simply right-click the entry for the device in the Bus Name column and select “Connect External Effect”. The icon is removed, and you can use the external device within your project as before.
Note that busses set up for external effects or exter- nal instruments are saved “globally”, i.e. for your par- ticular computer setup. “

I tried to do right click in bus name ecc… but doesn’t work!
Probably is caused by changing computer. Moreover in mac’s plug ins folder there are regular virus .vst and .vst3 …