With either TextEdit or Text Wrangler you could try to open up the file(s) in it.
http://www.barebones.com/products/textwrangler/
(Free )
Open up CSV 1 with one of those text editors
then open CSV 2,
select all CSV 2 and paste into CSV 1.
Save with different name. Use .txt or .csv as extention
I just created a 224 Mb cvs file with 950,400 lines and opened it with TextEdit as well as Text Wrangler. TextEdit actually seemed faster.
ALSO
Side issue, your MS Office 2011 may have become corrupted. Reinstalling Office 2011 can address problems that you may be experiencing.
The current version of Office 2011 is 14.4.8. You might try reinstalling MS Office 2011
First - find your Office 2011 install disc with the product key # - and only then remove Office according to MS instructions
http://support.microsoft.com/kb/2398768
Or go here to DianefromOregon's site for help removing Office 2011:
http://www.officeformachelp.com/2012/12/office-for-mac-2011-remove-office/
Then Reinstall from DVD
Then enter your Product #
After successfully reinstalling Office 2011, update your Office product using the Software update within Office called Microsoft Update or going to the Help menu within Word or Excel or PowerPoint and select Update.
It may take a few times before you get to final upgrade to current Office version. It should be 14.4.9 as of current date.
How to locate product keys
http://support.microsoft.com/kb/2279109
or here on locating product keys
http://office.about.com/od/MicrosoftOfficeMac/a/Best-3-Ways-To-Find-Microsoft-Of fice-For-Mac-Key-Codes.htm
Or
tp://try.officeformac.com/store?Action=ContentTheme&Locale=en_US&SiteID=msmacus& pbPage=CSTable&resid=VSGpKAoydBAAAINBCDQAAABU&rests=1428269373647
Note is updated as of April 21, 2015