When a customer has more than 50 workflows the workflow manager adds paging buttons. On any pages after the first none of the rows are clickable. They also don't have the "pointer" cursor. Dave Beech has reproduced this. I tested this on Chrome and Firefox in their latest versions (33 & 28 I think).
Workaround is to manually figure out the id of the job and construct a URL to edit it. Or to make a clone of the existing job and then delete the original one.
Tested on CDH 4.4.0 and CDH 4.5.0.