How bout Bulk insert?
http://www.sqlteam.com/article/using-bulk-insert-to-load-a-text-file
~hope this will help
There could be other reasons that resulted to the buffer overflow exception and not just the size of your csv file. Is this just a firehost insert, or you have transformations in the process? As there are other ways of doing this, lets try to solve it first with SSIS as this is the best candidate for the job.
i think that overflow is caused by BAD data in your csv.
i created a 6G csv file and import it to table using SSIS and it works fine. I used Flat File Source and Ole DB destination and No transformation, just direct import.