[Plugin: W3 Total Cache] Minify uri doesn't accept & amp;

I’m trying to minify an url like:

https://domain/wp-content/plugins/jquery-vertical-accordion-menu/skin.php?widget_id=2& skin=steelblue

The problem lies with the odd usage of & amp; in the URL, i’m not sure why this is used, however without minifying the browser accepts it and loads the correct file with the GET vars intact.
please ignore the usage of the space in between the & and amp;, but without a space this get translated to just &…
After minifying this URL, i get php errors in the minified CSS. These errors are because when minifying not all GET vars are used: the request is made for:
https://domain/wp-content/plugins/jquery-vertical-accordion-menu/skin.php?widget_id=2

As a solution i tried changing the URL to:
https://domain/wp-content/plugins/jquery-vertical-accordion-menu/skin.php?widget_id=2&skin=steelblue

which works for the minified CSS… however also leaves the original css file request in the head of my page (i presume that because the exact string isn’t matched anymore this particular line/request isn’t cleared from the page.

So, how can i get this to work properly?

Best regards,
Ruud