It depends on the level of corruption. If the power outage actually occurred while the file was open on the disk then it's probably not possible to save it.
You can check this by looking at the file size on disk. If it is zero bytes then the tasklist is gone completely. If it has a size then change the extension to .xml and try to load it with IE because IE is good at reporting where XML errors occur.
In addition to Auto SQA's comments, TDL saves another backup during the save process in case the process is interrupted: <tasklist>.bak.tdl, so it's worth seeing if you can find that too.