Snopes appears to have debunked the position, but I don't know if it's a partial debunking specifically applicable to plastic containers and frozen water in the microwave, or if it applies to saran wrap in the microwave, as the study that was performed by the high school student back in 2002.
Here is the snopes link:
http://www.snopes.com/medical/toxins/cookplastic.aspAlso, there was a valid study by a high school student that involved saran wrap, oil, and leaching that occurred with microwaves, but this article suggests that though leaching did occur, there is no harm as long as you use plastic which is FDA approved.
"According to FDA , “While it is true that chemicals used to make plastics can leach into food from plastic containers and films, all of the regulated chemicals used to make plastics for food contact, including DEHA, have been reviewed by FDA and have been found safe for their intended use.”
Although a real student named Claire Nelson did receive an award for a school project in the late 1990s, the award was based on her systematic approach to exploring a question, not for identifying a danger to human health as suggested in the e-mail hoax"
http://www.plasticsmythbuster.org/carcinogens.aspSo, the conclusion of the second article is that leaching does occur, but if you use appropriate regulated containers, you should be okay. That leaves out the obvious. What about containers which don't meet requirements, but you have no way of knowing?