Try pasting the path of the logo without clicking the 'Browse' button and then click 'Update Theme'
Is there a good solution for this? I have tried updating the Theme using a custom login logo, and now all the images are blank. i did copy and paste the path of the logo, and it appeared to work. After the IIS reset, my login page has no background and no logo. The images are in the LANDESK\BridgeIT\Content\images\ folder.