Text disappears when ungrouping WMFs or pasted drawings
When you ungroup an imported Windows Metafile (WMF) graphic or a pasted drawing, some or all of the text may disappear.
Try deleting a few slides from your presentation, then import or paste the graphic again to a new slide and try ungrouping again.
If you'd rather not delete any slides, start a new presentation, paste or insert the drawing into it, ungroup, regroup, then copy/paste the drawing into your real presentation.
Thanks to Brian Catlin, who reported the problem and found the solution. According to Brian (and thanks, Sonia, for verifying it), this only happens with larger presentations. In his case, there were 250 slides in his show. If he deleted a single slide then tried the ungroup again, it worked properly and his text stayed put.