Sorry guys. The problem was not in SQL Server. In order to see the text I copied it to Notepad. And ALWAYS got the same result. But after that I decided to use Right(myText, 100) to check and found out that whole text was inserted into the field. After that I add more data into the table and had no problem. Thank you guys so much for your help!
I was pretty sure something like that was what was happening. Thanks for the feedback.