SSL issue with COD module

[matezznet]

I use RapidSSL certificate for my domain, SSL access is allowed. The issue is when customer enter to https://DOMAIN/modules/cashondelivery/validation.php address then the pictures in header (logo.jpg and the language flag - readed from /img/l/flag.jpg) are called with http instead of https prefix. beacuse of that there is a warning message from browser that there is unsecured content on the page.

Also there is a issue with Categories block which is not probably called with https prefix (not displayed under IE8 when I allow to show just secure content).
I use also bankwire module - there is no issue and also other pages are ok.

When I switch from my theme to the default one - there is no change.
I use canin.sk/prestashop one page checkout module, but IMO it doesn't overwrite any files regarding COD.

I would kindly appreciate any hints where to look for the source of this issue. Many thanks in advance.

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UPDATED
Ok, I did a stupid workaround for pictures - I manually changed {$img_ps_dir} to {$base_dir_ssl}img/ in header.tpl and blocklanguages.tpl to force to use https each time for these pictures. But there is still remains issue for DOMAIN/js/jquery references which use http prefix instead of https one. If I understood well, $imp_ps_dir and others global variables are created in init.php but I can't find out what makes the difference among COD validation page and others.

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WORKAROUND
I didn't find the source of my problem. Therefore I created new COD module base on Cheque module and modified it a little bit for my purpose. I would like to know if it is only me who have the problem with COD v0.3 on Prestashop 1.2.5 using SSL or if it is only me - guys may you let me know ? Thx