It may not be that it's not recognizing the object. What it may be is that the scripts are running through faster than the actual installation process.
The general suggestion I always make is, after you record a test, go back and re-edit it and put in WaitWindow or WaitProcess or WaitAliasChild or whatever commands as appropriately, especially in cases where you click a button or link and then expect a different window to come up.
Considering the class of window you're asking about, this appears to be a window indicating to close the installation process. Most likely, if it's like most installation wizards, there was a process of copying and moving files around that takes some time before the close window is displayed. That process may take more or less time depending upon any number of factors so a hardcoded Delay call may not always wait long enough.
If you're already using one of the wait commands indicated above, try increasing the timeout setting within the command to something that is definitely longer than the average time for installation.
