If you are opening the log viewer in Altiirs server during the solution installation in SIM, you will see error message if the solution is not well-installed.
According to my experience, sometime the error is related to SQL tempdb, if this is the case, just repair the solution inside SIM will NOT recover the solution . Because SIM repair just repair the file/registry of the solution, but since during the solution installation, installer will trigger the aexconfig tools to create table column base on solution config file.
Same as Kyle, running C:\Program Files\Altiris\Notification Server\bin\AeXConfig.exe" /configure "C:\Program Files\Altiris\UNIX Agent\UNIXAgent.config" can ask the installer to write the table/column.
Regards,
Wallace