1) Welcome to the Party!
2) As you are obviously new here, I have some suggestions to help us all help you:
When you post, please post your entire configuration including (but not limited to) your installation method (7.X.X?) and vicidial version with build (VERSION: 2.X-XXXx ... BUILD: #####-####).
This IS a requirement for posting along with reading the stickies (at the top of each forum) and the manager's manual (available on EFLO.net, both free and paid versions)
You should also post: Asterisk version, telephony hardware (model number is helpful here), cluster information if you have one, and whether any other software is installed in the box. If your installation method is "manual/from scratch" you must post your operating system with version (and the .iso version from which you installed your original operating system) plus a link to the installation instructions you used. If your installation is "Hosted" list the site name of the host.
If this is a "Cloud" or "Virtual" server, please note the technology involved along with the version of that techology (ie: VMware Server Version 2.0.2). If it is not, merely stating the Motherboard model # and CPU would be helpful.
Similar to This:
Vicibox X.X from .iso | Vicidial X.X.X-XXX Build XXXXXX-XXXX | Asterisk X.X.X | Single Server | No Digium/Sangoma Hardware | No Extra Software After Installation | Intel DG35EC | Core2Quad Q6600
3) "8 core xeon with 8 Gigs of ram" is interesting, but other posts suggest you are likely using a virtualized server and not straight on the hardware of a server. If you check your provider's offering, you will likely find that you can rent a hardware-based server instead of a VPS, but it will cost real money.
4) "Predictive dialing with 3 agents" ... Virtual Vicidial is only for one to four phone calls. Each agent is one call, and every ringing or live call is another call. Virtual Vicidial will fall apart when timing isn't perfect.
5) You did not share your build method aside from the word "Vicibox" without a version, so I'm not even positive you used a Vicibox iso installer.
6) You could be experiencing any one of a myriad of system failures that delay ANY of the processes involved in Vicidial ranging from DNS to MySQL or networking. Check your logs for errors on all systems with logs. But if it's virtualized ... that's your problem right there. Build it in hardware for outbound to stabilize.