Golfscript, 20
26,{.97+\{.}*}%=42`*
with new line, 21 chars (by Nabb)
26,{).[96+]*}%n+=42`*
Actually Nabb beat mine, here is original solution for with new line, 22 chars
26,{.97+\{.}*}%n+=42`*
This is simply generating source string and just comparing it against string from stdin.