This problem irritates a lot of people, including me sometimes. The background on it is on some windows systems, possibly most often back on Win95, really large files when displayed within TextAloud would eat up huge amounts of windows resources, sometimes causing crashes, so we hard coded in a limit.
The good news is TextAloud 2.0 shouldn't have this problem, and even in current versions, there is a way we can turn off the limit for you. Email email@example.com
and ask for the instructions to turn off the import limit. We'll email you back a small file that will turn off this limit.