Do you know what versions of PHP and mySQL you are using? The requirements for 1.5 and 1.7 / 2.5 are different. Older versions of your hosting software may not work as well with newer versions of Joomla.
www.joomla.org/technical-requirements.html
The difficult we do immediately, the impossible takes a little longer.
I'm using PHP version 5.3.8 and mysql version 5.0.51b. I can successfully install verison 2.5 and 1.7 if its just a regular copy of Joomla. The issue is when trying to use your 1.7 rocketlauncher.
I'm not sure what's happening, it has to be related to your hosting account. Out of all of the posts in the forum, this issue has only been reported a few times and none of our developers or moderators have ever been able to re-create it. It's not an issue with the Rocket Launcher.
Problem: Error when installing sample data - Table '(DatabaseName).sxeht_usergroups' doesn't exist
Joomla 2.5 / Reflex Template with Rocket Launcher
I tried everything I could find on the forum including manual INSERT TABLE SQL query. Nothing worked.
What I finally did that did work was decompressing the rt_reflex-rocketlauncher.zip locally and uploading all the contents via ftp to my server directory. Sample data was installed successfully without issue.
Previously I had uploaded the rt_reflex-rocketlauncher.zip via ftp and decompressed it via the Webshell file manager on the server. Faster? After a day of trying to get things working, much slower.
I have no clue why decompressing on the host server would make a difference but trust me, it did. If anyone has a clue, please post because this issue has been popping up for a long time.
In any case, hope this helps someone else in rocketlauncher hell.