The file options.txt contains the following URLS which are wrong in the current version:
<label for="expand3"><img src='<?php echo get_settings('siteurl') .
"/wp-content/plugins/collapsArch/" ?>img/collapse.gif' /> <img
src='<?php echo get_settings('siteurl') .
"/wp-content/plugins/collapsArch/" ?>img/expand.gif' /></label>
The (sub)directory name "collapsArch" is wrong because the plugin is installed in subdirectory "collapsing-archives".