Always use together builds of the same type and from the same date.
All NetBeans based products should be able to work together, of course. There is no guarantee that all possible combination of all the available builds will work together, because the source code/modules are changing during the product life cycle/phase. The only thing that should definitely work together are builds of the same type from the same date (or "around" the same date).
For example, you have NetBeans IDE 5.5 Beta 2 installed. Then you can add all "beta2" packs to it (but not "beta" packs).
NetBeans IDE 5.5 Beta 2 Installer works with:
When then for example NetBeans IDE 5.5 Release Candidate 1 becomes available, the latest recommended combination of builds is "only install RC1 builds together", etc.
If for example Enterprise Pack 5.5 RC1 is not available yet, try the daily builds or milestones that are closest to the release date of NetBeans IDE 5.5 RC1. Note: Try this workaround only on a copy of your projects, we cannot guaranty that this will always work!
Applies to: NetBeans IDE 5.x
Platforms: All
See also: NetBeans installer download