If the laptop used to resume from hibernation without problems earlier, and this is just a recent problem, then it could be due to disk issues like fragmentation, or corruption in the hibernation file.
First, run chkdsk /r at the command prompt to eliminate file system errors. A reboot maybe required.
Run a disk cleanup to get rid of junk files, and run a proper defrag. Use a powerful defragmenter like Diskeeper 2008 Pro to defrag the disk. You can grab free trial versions from
http://www.diskeeper.com for the job. It's an awesome program for defragmenting hard drives.
Also, it would be a good idea to disable hibernation before the defrag, so the hibernation file is deleted and then re-enable it after the defrag to create a new hiber file. This will allow defrag to run smoothly and thoroughly.