If you're using a version - Acid 1.2.0 ( most likely something like 1.1.13 ) here are the instructions to upgrading.
The instructions may seem like a large piece of text, but I'm just trying to be explicit about every detail. Updating really isn't that difficult and takes only a couple of minutes.
http://themeforest.net/item/acid-unique-horizontal-blog-and-portfolio-theme/4508779
TO MAC USERS: If RAR password doesn't work, use this archive program:
RAR Expander 0.8.5 Beta 4 and extract password protected files without error.
TO WIN USERS: If RAR password doesn't work, use this archive program:
Latest Winrar and extract password protected files without error.