I do not know what local complications might underlie the voting patterns in the Glenrothes by-election, but comparing 2005 & 2008 in the simplest possible way shows the following:
Changes in votes 2005-2008
Labour +500
SNP +4,500
Con+Lib - 5,000
The Rest - 1,000
Total votes cast: 2008 36,000 2005 37,000
Though obviously not a thumbs down, I do not see how this can be interpreted as a vote of confidence in the handling of the economic crisis. It looks more like a polarisation into a straight fight between nationalists & unionists