I tried this out on my computer, and yes it does seem that there has been a validation rule added to force the prefix to start with a letter.
This is caused by the regex rule in
/installation/models/rules/prefix/prefix.php
//line 24
Code: Select all
protected $regex = '^[a-z][a-z0-9]*_$';
Which is due to /installation/models/forms/database.xml
Code: Select all
<field name="db_prefix" type="text" id="db_prefix" class="inputbox"
label="INSTL_DATABASE_PREFIX_LABEL"
default="jos_"
required="true"
/>
Which was changed to
Code: Select all
<field name="db_prefix" type="prefix" id="db_prefix" class="inputbox"
label="INSTL_DATABASE_PREFIX_LABEL"
required="true"
validate="prefix"
message="INSTL_DATABASE_PREFIX_MSG"
/>
Essentially by changing the field type to "prefix", it causes the prefix rule to validate the field. So you can either adjust the regex string in prefix.php, or change the field type in database.xml to get round this issue.
Sounds like this should be reported as a bug on the Joomla CMS tracker
http://joomlacode.org/gf/project/joomla ... er_id=8103