Old 32-bit plug-ins, filters, effects, codecs and so on won't work in CS5. Most vendors are updating their current plug-ins to be 64-bit, but some old ones are going to go the way of the dodo. Such is progress...
32 bit plugins will not work. The 3rd party vendors need to update their plugins to be 64 bit / compatible with CS5. Some have already done it; others are working on it. You would need to contact the 3rd party vendors to discover the status of their products being compatible with CS5.
Edit: Colin is just faster than me......
You cannot use the old 32 bit filters in CS5, they need to be 64 bits filters.
For Trapcode have a look at the Red Giant website. Upgrades will be coming soon.
Three in a row