Merriam-Webster's Third New International Dictionary (NI3), first published in 1961, was published on CD-ROM for the first time in 2000. I am afraid this CD-ROM is going to become a crucial factor in GAMES Magazine word-building contests. During my attempts to improve my score on a GAMES contest, "Lucky 13", which was current when I wrote this node, and in attempts to solve some particularly fiendish NPL puzzles and other subsequent puzzles and contests, I found a few errors in the CD-ROM version of the dictionary:

creeping pholx
A typo for creeping phlox, a plant. Spelled correctly in the print edition.
axis deeres
bony coales
These false plurals resulted from entry words that have multiple forms (axis and bony being the first entries for axis deer and bony coal), which simply have -ES listed as the plural form. Presumably some sort of automated system was used to add plurals and verb inflections to the word list, and it mistakenly applied the -ES to both forms. To the extent that the plural isn't explicitly made clear, these could be considered errors in the print version of the dictionary.
unvertifiability
A typo for unverifiability. Or perhaps a weird self-descriptive joke, since this spelling certainly has unvertifiability. Spelled correctly in the print version.
contesseration
This word is spelled fine, but in its definition, friendship is misspelled freindship. Spelled correctly in the print version.
according to the legs involved anterior biped
constructive malice; distinguished from malice in fact
peroxydisulfuric acid; not used systematically
zinke; compare serpent
and others
These errors appear in the entry word list that searches use, which includes terms that appear in the called also section at the end of some definitions. In some cases, when this section includes explanatory text or multiple terms, odd phrases like this were cataloged as "words" and come up in some searches. (I was searching for very long words and phrases when I first found some of these, but I believe every entry containing a semicolon is an error of this type.)