I received this error on uTorrent a few days ago.
"Unable to save the resume file. some data may be lost.
Another program might have the file open, or the disk is full. please correct this and click retry. If you press cancel, the resume file will not be saved."
Really scare you out when you are still downloading a few gigabytes files and the status was 80-90%.
Advise from uTorret FAQs :
How do I fix Error: Unable to save the resume file?
Simply create two blank files named "settings.dat" and "resume.dat" (without the quotes) in the same folder utorrent.exe is saved in. Make sure Windows is not hiding the file extension when creating the file (in Explorer, Tools -> Folder Options -> View, uncheck "Hide extensions for known file types", hit OK)
But I didn't find all that files in uTorrent.exe folder. You can find it in :
c:\Documents and Settings\Your Name\Application Data\Resume.dat.old
If you ever try to tweak the uTorrent, please remember all the settings before you perform this fix.
Just delete resume.dat.old, resume.dat, settings.dat and settings.dat.old. After that create a blank files by opening notepad File>Save As and type in resume.dat.old, File>Save As and type in setting.dat.old, File>Save As resume.dat and File>Save As setting.dat
Please stop the uTorrent service when you do this!
If you find another error message that says :
"Cannot delete resume.dat: The file or directory is corrupted and unreadable."
Try to run chkdsk. Start -> Run -> chkdsk /F C:
Click yes when it asks, then reboot.
Also, you may check out Bit Defender. Sometimes it can causing the problem to uTorrent.