Apache2 fails to start after adding new domain

I have an odd problem with virtualmin on a debian server; when I add a new domain, everything seems to go well, but then I find that apache has stopped; on investigating it appears that a lock file has been placed in /etc/apache2/sites-enabled with the name of the domain and apache attempts to read it, failing with an error like this (for a domain of ‘example.com’):

[pre]Syntax error on line 1 of /etc/apache2/sites-enabled/example.com.conf.lock[/pre]

Does anyone have any thoughts about how I can check whether this is a virtualmin bug or something else?