You can try later versions of LibreOffice (3.6.2 is declared stable) and also the latest version of Apache OpenOffice, AOO 3.4.1.
If your colleagues are using the new version, Office 2013 Excel, the best route may be to have them save the documents as ODF for you.
Another alternative is to upload the .xslx files to SkyDrive by creating an account at http://skydrive.live.com. You can then view and edit them in a browser (Internet Explorer, Firefox, or Chrome). You don't need Microsoft Office installed. You'll be warned if a spreadsheet uses features not supported by the SkyDrive versioin.
In all cases, you will have to experiment to see which routes provide the greatest preservation of fidelity in the spreadsheets.
Your colleagues who have Microsoft Office can obtain them back directly from SkyDrive and also save them to SkyDrive from current versions of Office, if that makes it easier for you (and for all of you when not in the office). You'll probably want to create a folder in which only those live.com accounts that you give permission can see and/or edit the documents.