It's been a while since I have done any proper work on the tag cloud as it has been quoted as working very well, however, I have had feedback with foreign characters such as German/Spanish specific categories. Apologies in advance for it taking me so long to get a fix out but it's been difficult to test as not all servers support the correct enctype. Before using this, ensure utf8 is being used.
The problem lied in the regex being used to strip out non alphanumeric characters and this has now been fixed. This is the only bug fix in this release, however, I always appreciate feedback.