top reports 9999% process CPU utilization

I have set the top sampling interval to 60 seconds (just press "d" in top, then enter 60).

Monitoring top reports (try also pressing space after setting new interval, to refresh the top report), I noticed that top is reporting 9999% CPU utilization for a process, which is obviously wrong. This does not happen with regular top intervals of 3 seconds.

Please find a screenshot attached.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: procps 1:3.2.8-11ubuntu6
ProcVersionSignature: Ubuntu 3.2.0-41.66-generic 3.2.42
Uname: Linux 3.2.0-41-generic x86_64
ApportVersion: 2.0.1-0ubuntu17.2
Architecture: amd64
Date: Thu May 9 10:00:39 2013
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: procps
UpgradeStatus: No upgrade log present (probably fresh install)