Login to admin panel does only work after deinstallation of the plugin

Hi kubi,
I use your plugin for some years now I guess. But today I noticed that I could not login into my admin panel anymore. Above the login form there were some following infos:

– Warning: chmod() [function.chmod]: Permission denied in (path to plugin”change-uploaded-file-permissions”) on line 93
– Warning: Cannot modify header information – headers already sent by (output started at (…) /wp-content/plugins/change-uploaded-file-permissions/change-uploaded-file-permissions.php:93) in (…)/wp-login.php on line 368
– Warning: Cannot modify header information – headers already sent by (output started at (…) /wp-content/plugins/change-uploaded-file-permissions/change-uploaded-file-permissions.php:93) in (…)/wp-login.php on line 380

When I tried to login it was not possible – I saw even more infos like the mentioned. Then i renamed the plugin folder and afterwards login was possible again. Then I deactivated the plugin.
But after deactivation i noticed that several images were not shown in the frontend! Is it possible that only the images that the plugin rewrote the file permission rules are not shown anymore if the plugin is deactivated?

Any ideas? Maybe my site was hacked or something other happened that is not caused by the plugin itself – but wanted to try to contact you if you have any hints for me regarding these problems.

Big thank you!

http://wordpress.org/extend/plugins/change-uploaded-file-permissions/