Can't open Skype at all on Macbook Pro

I have been struggling with Skype for a long time on my Macbook Pro and wondered if anyone has any advice. When I try to open the application, it crashes immediately before I can even log in. This has been the behaviour for several versions of Skype now, so I am starting to think there is something on my machine which conflicts with it and the problem will not be solved by waiting for a future release of Skype.

Currently it is failing with version 6.0.60.2496 of Skype (downloaded today) on a MacBook Pro running Mac OS 10.8.2. The machine is a 2.53 GHz Intel Core 2 Duo with 4 GB of RAM, purchased in 2009. Exactly the same problem occurred in Lion, before I upgraded to Mountain Lion.

I have tried a number of steps to solve the problem, including:

* Removing the /skype folder from /Library/Application Support and the preference file from Preferences, uninstalling Skype, restarting in Safe Mode, downloading it again, installing and trying to open it

* Changing the settings in Text to Speech to a different voice

* Downloading an older version of Skype and trying to run that

Everything crashes instantly every time and I am unable to use Skype at all.

Skype support have told me there's nothing further they can suggest and they think it may be a conflict with my System fonts, but I am desperate for any advice from someone who has encountered (and hopefully solved!) a similar problem.

Many thanks in advance for any help you can offer.