There are at least two newer versions of ID out there so you would need to update your install to one of those. Since you have only ID 5.5, your machine knows it's an ID file but will only tell you it's a 5.5 file because that's all it knows about.
Are you fully patched to 7.5.3? If not, do it and then try to open the file
again. If it's a file created in a later version of ID you'll get a much
more accurate alert.
How do you know it's a CS5.5 file?
It's most likely a file from a newer version of InDesign, InDesign Cs6 or InDesign CC.
Go back to your source and ask them for a IDML file using File>Save As and also a PDF so that you can check text issues, like reflowing of text etc.