If I open a Plain Text window and paste in the following line of text, TextMate 2.0.3 CPU usage goes to 100% and never stops. Syntax highlighting ends at the line containing the text. Here's the string:
ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~:/?#[]@!$&'()*+,;=