I'm having the same issue as well. An uninstall and then re-install worked for about a week, but the problem is back. I tried clearing temporary files, but that didn't make a difference. I also noticed that it will occasionaly perform the search without crashing, but it doesn't point you to what you were searching for. For example, if I search for "blue", it would take me to the word "red" in the document.
We are seeing the same with several of our PCs here. Uninstalling and reinstalling will not correct this. Neither will updating to 9.1.1
The search will either cause Adobe Reader to crash, or it will select the wrong word.
Also, I noticed that if we try a Full Reader Search, in the left column it displays an error message "There was an error retrieving text." instead of search results.
This appears to be affecting PDFs created by an app called "Active PDF Toolkit"
If we use Adobe Reader 8 and earlier, everything works normally.
The only fix I have found is to try another reader instead. I'm using Firefox, which has proved stable.
I hadn't tried a Full Reader Search, so I don't know (and now I will not know) whether I suffer the same fault "Brachus" suffered there.
While it's in some (perhaps perverse) way comforting to know I'm not alone, I remain puzzled by the lack of profile this fault has on the internet.