In several articles, revision text from early 2005 appears blank when viewed in the English Wikipedia. IIRC the blank revision text appears around the time that Wikipedia changed its compression formats. This has been discussed several times on the English Wikipedia village pump; the URLs below contain plenty of examples of this problem:
Version: unspecified
Severity: major
URL: http://en.wikipedia.org/wiki/Wikipedia:Village_pump_(technical)/Archive_65#Blank_sequence_of_pages_in_an_article's_history