Upon installing, the installer does not properly copy all files from the package.
./Sources/Subs-Package.php
2: copy(../community/Sources/sd_plugins_source/front_page/index.php) [<a href='function.copy'>function.copy</a>]: failed to open stream: Not a directory
2: copy(../community/Sources/sd_plugins_source/front_page/SDPluginFrontPage.php) [<a href='function.copy'>function.copy</a>]: failed to open stream: Not a directory
2: copy(../community/Themes/default/images/simpledesk/attach/video.png) [<a href='function.copy'>function.copy</a>]: failed to open stream: Not a directory
2: copy(../community/Themes/default/images/simpledesk/attach/blank.png) [<a href='function.copy'>function.copy</a>]: failed to open stream: Not a directory
...and so on. 8 pages of errors just from the installation. I don't know if it's just the way my server is configured, or a bug with the Package Manager, or a problem with the SD installer. But it does seem to be a problem with embedded directories/files that are deeper than the ones included in the package-info.xml
It's the way your server is configured and virtually every complex mod will have trouble.