I have been having the same issue with Turbotax Premier on a desktop Mac. Changing the password has not worked; deleting all the caches and cookies for both Turbotax and Merrill has not worked I have checked the sizes of the files, and my 1099 in .pdf is nowhere near the limit (400 kB for 110 p) and the .csv file, which might be the format for Turbotax imports is only about 300kB. Merrill Lynch support was of little help and simply referred me to Turbotax. Turbotax support has been completely useless, only suggesting I enter the summary data manually and mail a paper copy of the complete 1099 (about 120p) to the IRS for processing prior to filing electronically.
