Cell phone video often uses a variable bit rate, such as from the iphone... these links are about iphone video, but they may help
http://forums.adobe.com/thread/881246
-and http://forums.adobe.com/thread/1011411?tstart=0
-and a fix http://forums.adobe.com/thread/934466
If those links don't help, more information might help
What are you editing, and does your project match your video?
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Read Bill Hunt on a file type as WRAPPER http://forums.adobe.com/thread/440037
What is a CODEC... a Primer http://forums.adobe.com/thread/546811
What CODEC is INSIDE that file? http://forums.adobe.com/thread/440037
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Report back with the codec details of your file, use the programs below... a screen shot works well to SHOW people what you are doing
http://forums.adobe.com/thread/592070?tstart=30
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For PC http://mediainfo.sourceforge.net/en or http://www.headbands.com/gspot/
Also, to be sure your video matches your sequence, read on...
For CS5 and later, the easy way to insure that your video and your project match
See 2nd post for picture of NEW ITEM process http://forums.adobe.com/thread/872666
-and a FAQ on sequence setting http://forums.adobe.com/message/3804341