I got some feedback from my PowerPoint TTS blog that a couple of people were having problems getting it to work. In an attempt to keep my readers happy, I wanted to make sure my code and insructions were correct. I verified my instructions, using Office 2003, and everything works as I noted. But, to expand on the instructions a bit, focused on the problems noted, it sounds like the reference hasn't been set. From VB, when in Module 1, verify that the following references are selected. In my case, all of these were selected by default, except "Microsoft Excel 11.0 Object Library". You should have the following selected, in the following order of priority (not sure if that matters though):

1. Visual Basic for Applications
2. Microsoft PowerPoint 11.0 Object Library
3. OLE Automation
4. Microsoft Office 11.0 Object Library
5. Microsoft Excel 11.0 Object Library

So if these references are selected in VBA, then please take a look at these Knowledge Base articles for further assistance.

1. How to automate Excel Text to Speech in another Office program 
2. XL2002: "Run-time Error 1004" When You Attempt to Use Text to Speech in Macro - Sue Waetzig, and maybe David H, based on this article, I think you may not have installed the Text to Speech feature in Excel. To fix this, run Setup again for Office and select Custom during the setup wizard, then make sure all of the Excel features are selected during setup.  

Please let me know if this helps!