Solution for PKS Load XML Error: an invalid character was found in text content. This error can occur from WinNonlin, when an invalid character is entered in the Study Description field of a study. This can occur, for example, by copying and pasting an unusual symbol, such as a superscripted copyright symbol, into the description. The error occurs if the character cannot be rendered in the WinNonlin study catalog. The problem can be resolved by having the admin log in via the web browser and delete the invalid character using Modify Study Information.