More Murphy's Law of Presenting With Technology

In response to my recent post about how Murphy's Law (whatever can go wrong, will go wrong) definitely applies when presenting with any kind of technology, from a projector to a phone, a few readers sent in comments: 

From LG on the human error side of Murphy's Law: 
"Great examples, and oh so real.  Here are my contributions:
  • Forgetting to plug in the laptop, so it quits during a class, giving a last gasp about a dying battery.
  • Forgetting my power cord back at the home office and having to ask others to scurry around to find one that matches my laptop.
  • Forgetting that I have muted my phone during a web class (while participants are doing a quick exercise), then talking. Participants saw my lips moving on my web cam but couldn’t hear me.
  • Having an earlier, uncorrected version of my presentation on my laptop. This has happened when somehow I saved an open presentation to a flash drive, therefore saving it without the changes. (Can’t quite explain it, but it has happened. I compose on my desktop PC, then use a flash drive to get the presentation to my laptop.)
  • Forgetting my remote, so having to tether myself to my laptop rather than being able to move around as I like to do."

From Michelle: 
"A good follow up would be ways to avoid the Murphy Law effect:
  • I always make printouts of the presentation to avoid any PowerPoint issues. Having two sets of remotes can be handy too.
  • Wirehead set – know how to quickly transition to a regular handset or other means."

Thanks LG and Michelle for your comments!  

What other examples have you seen or experienced of Murphy's Law of Presenting With Technology?