query vars does not work since 2.7 upgrade

Hello,

I use custom query vars, defined with the ‘?’ into the url.
Eg:
http://www.blablfqf.com/?my_custom_var=a_value

I have upgraded in WP 2.7, but the get_query_var(‘my_custom_var’) does not seem to work at all.

This was working in previous version 2.5

Strangely the query var passed with the slash ‘/’ are still working well
http://www.blablfqf.com/tag/car/

Any idea of what’s wrong? (option in 2.7, changes ?…)

Thanks in advance for helping