....when Itry to project the shapefile again,...
my guess is since you mention projecting again, that the shape in question was projected before this started happening. It may help others to know
- version of the software?
- what did you project from and to...and did you make sure the source was really in that projection and not just "assigned" a projection.?
- what command did you use to project (or again, did you just try to assign a projection without really projecting...we see that sometimes on the forums)?
- where are you saving the shapefile (if really a shapefile, make sure it is not in a fgdb folder)?
- a graphic of what it looks like before is disappears, and after (assuming other layers are still showing) may help other see if it is a scale-display issue or a projection issue.)
As far as ArcCatalog crashing, I second Jayanta's suggestion to reset your profile.