What I tried:

1. Define a form using Period characters (.) in a template name in the page name parameter in the info-method, e.g. "{{{info|page name=<Event.Set[Superactivity]> <Event.Set[Title]>|create title=Add Event|edit title=Edit Event}}}"
2. Create an article using that form.
3. Save the article.

Result:
PHP error: "Fatal error: Call to a member function exists() on a non-object in C:\xampplite\htdocs\w\extensions\SemanticForms\specials\SF_FormEdit.php on line 205"

Configuration:
XAMPP with

MediaWiki 1.15.4
PHP 5.3.0 (apache2handler)
MySQL 5.1.37
Semantic MediaWiki 1.5.0
Semantic Forms 1.9.1 (& 1.9)

Version: unspecified
Severity: normal