The sample configuration files loaded by install.pl are matched to the asterisk version. Your old box had asterisk 1.4, your new box has asterisk 1.8. Moving the database means your asterisk version in the DB (admin->servers) is for the old server, so vicidial would issue 1.4 commands instead of 1.8 whenever it referred to this data source (php or perl scripts, either may do so). The astguiclient.conf file has an asterisk version to tell the installer which sample files to copy, and this is also available to most pl scripts and possibly to php scripts as well ... and if you brought the configuration files from the old server, this would also have 1.4 and your asterisk configuration files would be for the wrong version, causing syntax errors among other possible problems.
When porting a Vicidial install from one server to the next, you need to bring:
Client audio files (/var/spool/asterisk/monitorDONE)
Audio Store files (if you loaded any)
Any custom files (those that are not actual vicidial files, ones you created yourself) and DIFFs of any Modified files (so you can re-modify the new vicidial files)
Database
Note that if you bring the asterisk library sounds (var/lib/asterisk/sounds) from the old server to the new server, there is a chance that you will overwrite a newer file with an older file ... so you'll want to be sure to keep the newer ones by performing a bit of a shuffle during the copy process.
The same concept applies to any agi scripts (var/lib/asterisk/agi-bin).
The client audio files should have been pushed to an ftp/web location (thus no need to actually copy them, as they are now on an external web server ... but if not, an rsync will do). Same with the Audio Store but be sure to create the folder with the proper permissions since the new server will not have that old server's folder.
Custom files have to be handled carefully, to be sure they will work with the newer version. Each will have its own criteria, of course. Especially if you modified previous files and have to DIFF them. If you have not modified any files, it is much simpler to just bring the DB and let the "install.pl" handle the file dispersal after the asterisk version is correct. Oddly enough, this was already true on the new server before installation ... except for the value in the DB (which is easily changed ...). It has been observed that the the asterisk version in admin->servers may need to be FULL in asterisk 1.8 (as in something more like 1.8.x-vici instead of just 1.8, from the asterisk -R version information).
The database has to be upgraded before or after the move to match the db schema of the installed code in the final location. It also must have the proper IP address in several locations (which is where the script comes in).
In short, it is not a simple task, but it is "doable", as you're finding out. It's also quite educational.