Well, hard to say whats going wrong with your DM800se...
I would suggest you make a clean, new installation, do not install any skins or plugins, do not restore any backups. Just make a clean installation, use the wizard for the settings, and then try again the zapping...
I'll bet your problem will be solved.
Good Luck!

Just to make sure: We are talking about fta, aren't we? Then this isn't a normal behaviour. And it's better when you use an older software or does this problem persist in any software revision (maybe more or less)?

If it isn't fta, the slow zapping might be an issue of unsupported software and you should look somewhere else for help, first.