I don't know which version of Poser you use, but I've found that with Poser 5, I just start with one of the basic run/walk animations (or a combo of two or more), and when I apply it to the model, I set it for 30 frames (which is what the default Poser walk and run animations are), and to "walk in place" as well as repeat only once.
Once I apply those settings, I then go to the "animation" menu and chose the option "Re-Time Animation" and set the source frames to 1 for the first and 30 for the last, and the destination frames to 1 for the first and 15 for the last... What that does is compress the animation into the first 15 frames, but you'll still have to delete frames 16-30 (just click on the box on the animation toolbar that has the number of the LAST frame and change it to 15).
I've never had any trouble using this method.
....Of course, with carying items with two hands, or other objects that need to have less arm movement, you'll have to modify the appropriate arm settings... For carrying rifles or staffs in both hands, I just record all the settings for both arms (shoulder, forearm and hand), then go into the almost-finished run animation, set the arm parameters, and delete all other keyframes associated with the arms (use the "graph" option for this, otherwise you'll delete the keyframes for the WHOLE figure, rather than just one part of the figure or a single parameter.... Granted you'll have to delete all keyframes for each parameter, but at least you can do that by selecting ALL the keyframes and just pushing the delete key... then all you have to do is click on the other paremeters while you have the graph window open, and it'll automatically switch the graph to those parameters with the selection still in place.....)
I agree that the Run animations are a Chore to tweek.
), and like the old saying goes, "Good judgment comes from experience, which in turn, usually comes from bad judgment." 
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