hmmm... does Z work?

It would be very unusual for a chip to fail, these line drivers can take a lot of abuse. You could unplug the BoB from the PC and exercise each pin 2 - 9 to ground and to +5v with a bit of wire and check the voltage at pins 2 - 9 of the HC541 and the matching outputs 18 - 11 and see that they are as expected.

Its def an HC541?... you've not got the 541 and 244 swapped over (which would give exactly those symptoms i.e. 2 work, 2 dont)

Irving...