Just to follow up on this: Sarahhashmi sent me an example experiment. There was a bug in iolite that if you tried to set the color of the 3D plot using an 'orphaned' channel, it would cause iolite to hang. I have written a fix for this that will be available in the next release of iolite (v4.5.2).
One thing to be aware of is avoiding orphaned channels in the first place. You can do this by clicking the small wrench icon in the top left of the DRS view, and checking the 'Clear all channels before crunching' option (shown below). This will clear out all intermediate and output channels before the DRS runs. This avoids the issue of channels hanging around from previous runs of the current DRS or other DRS.
You should only keep this option unchecked if you're trying to apply two or more DRS to the same dataset (e.g. Trace Elements and U-Pb) but you should be aware of what you're doing and remove channels if/when needed.
One example where you could build up orphaned channels in a not-so-obvious way is to change reference materials and re-crunch the Trace Elements DRS (without checking the checkbox described above). If there are accepted values for the first RM and not the second RM, you'll end up with some channels that are out of date and/or empty. For example, if you were to use NIST610 for the first crunch, and you've measured U238, you'd get a U238_ppm channel. Then if you switch to some other reference material that doesn't have an accepted U value, and crunch the DRS again (without that setting described above being checked), you'll still have a U238 channel, but it won't have been updated by the most recent crunch. This can leave it empty, or worse, you may have changed your baseline selections (and hence baseline splines), or make some other changes, and the values in this channel won't reflect that.
So, TL;DR, check this box unless you are deliberately running multiple DRS!
If you have any questions about the above, please feel free to post here.