BLUF: Should I include on my a resume a position that I held for just five weeks?
When a recent layoff occured, my boss's boss saved me and found me a lateral-move position in another part of the organization. About five weeks later, the head of the department resigned and I was promoted to his role. So, my resume now shows a position that I held for, essentially, a month.
Proposed solution: fold the position that I held for five week under the description and accomplishments for my current job with a statement like: "assumed transitional project manager role from Sept-October 2009..."
I would appreciate your feedback. It is troubling to lose 3-4 lines of space on my one-page resume for a job in which I did not accomplish much.

Include it
It takes up extra space, but I would assume you were extraordinarily effective in those 5 weeks. It's a great conversation topic, and may prompt interviewers to ask you about something which is overwhelmingly positive. To be selected after a month on the job over and above everyone else is a great achievement.