DotNetNuke 5 introduced a new method of installing modules.  The new installer has  caused many issues for larger module packages.  Two commons issues are:
1) Installation failed due to SQL timeout.
2) Installation complete, but files not updated.

Active Forums and Active Social have had problems with issue number two.  The best way to check is to make sure the Control Panel indicates the same version you installed.  If it doesn't, you can simply re-install the module or manually copy the .dll files to your DotNetNuke bin directory.  This will this fix most errors that immediately appear after an install.