I’m using the wordpress plugin v 1.0 with WP 3.4.2
After much detective work (I’m a mere hobbyist re: sql databases and ajax), I figured out that having quotation marks entered into one of the cells prevented a previously working spreadsheet from appearing. I was just getting a blank page.
Finally figured out which rows were preventing loading and deleted them in the database. Everything is now working again.
The only error noted was a syntax error: unexpected in row 1878 of spreadsheet.php
Hope this helps others!