Dear Stefa, you can also apply the fix provided by Joomla but not yet included in an official distribution/
As you have perhaps seen on Joomla website, this is bug cause problem to many existing extensions.
I am just surprised that Joomla has not yet distributed a new Joomla 1.5.11 to fix it.

The manifest file is an XML file present in the root of the administration of the component xxx directory.
In this file, you will find 2 lines <installfiles /> and <uninstallfiles /> that are empty.
The bug in Joomla is that those XML tags can not be empty.
When removing those lines, this work.

You can also contact the author of the extension and ask him to fix its manifest files to avoid this issue with Joomla 1.5.10