I have MarketPress Lite installed and I noticed that I kept getting a white page of death with only the words "Service Unavailable" in the output. This occurred when I tried to visit a page that what set up with the slug "services". This also affected all the child pages under services (e.g., myurl.com/services/, and myurl.com/services/first-service/, and myurl.com/services/second-service/, etc.).
I worked around it by renaming the slug to 'my-services' (and not what my client wants).