Users of the Apple iPhone 4S are complaining about a poor battery life.
Many say their battery life is less than 12 hours on a full charge, with the capacity declining fast even when the phone is asleep - by as much as 15 percent an hour, say some.
"I lost 23 percent in about thirty minutes this morning - using the regular Notes app!" says one poster on an Apple support forum.
"I wasn't surfing the web, playing games, or anything like that. Just typing in the Notes app."
One possible reason for the bug is the location services feature in Apple's iOS 5 operating system. According to iDownloadBlog, the Setting Time Zone function keeps the location tracking circuitry running constantly, causing a significant drain in battery power.
It's possible to turn Setting Time Zone off, through Settings, Location Services and System Services. It means the phone won't keep track of time zone changes, but could extend the battery life considerably - although some users say they've ried this and it hasn't helped.
Others have suggested that the battery drainage could be linked to Diagnostics & Usage, with some saying their phones appear to be sending as many as 100 messages to Apple per day.
Apple's said to be investigating the issue.