Thanks for the uber-fast reply Krish. I looked at the key definition thing (k switch) but it didn't seem to to work either. Using what you gave does the right thing, only, when I transpose that command to use on my live data, it doesn't. Here's an example (first 10 lines out of the newly sorted file):

sort -t";" rk2,2 mwreport_joined.txt > mwreport_sorted.txt

GLMLRP_ComparisonJob;989:13:42
GLMLRP_Diff_HighlighterJob;989:08:56
AD046;988:44:15
GleamMIPostCanadaExtractJob;9196:53:12
GleamMIAGREERepAllBackOutJob;9025:39:12
GleamMIAGREEProdFacilCombJob;9025:29:36
GleamMIAGREEExcRateHistExtractJob;9025:21:26
GleamMIAGREEDynamicParamJob;9025:19:10
GleamMIAGREEClassExtractJob;9025:11:35
GleamMIAGREEClassPODLoadJob;9025:09:43

As you can see above, the "9196:53:12" value in the fourth record should be top of the list as it is the largest numerically