Was having trouble printing some 5167 Return Address labels using gLabels. The alignment was significantly off in my set-up using the default predefined template installed with gLabels on my Linux Mint LMDE netbook.
In comparing the template definition file with the stock measurements I found several things to be off slightly. In addition, my Samsung ML-2851ND laser printer appeared to be shifting the page image a bit also.
I created a custom template, adjusted for what I was experiencing, and now I can print consistent cleanly formatted labels within the stock outlines. Should you be experiencing similar issues, you could use my custom 5167 template. Just save into a file named as your_filename_here.template in the location set by your distribution (for Linux Mint LMDE, I discovered that was in ~/.confg/libglabels/templates).
BTW, should you need to customize the template further, see this documentation.