I have fond a bug on Magento CE 1.8.0 and 1.8.1 that is related to special price.
If I set some special price on product and save that change, magento sets current date for Set Product as New from Date (news_from_date), Special Price From Date (special_from_date) and Active From (custom_design_from). After these values are set I'm unable to remove them both grammatically and using admin panel.
Has anyone found reason for this issue and how to fix it.
P.S. This was ok on CE 1.7.2
It's a real bug, which a had in every update 1.8 and 1.8.1. This is the (temporarely) solution. I found it here:
http://www.sdms.it/magento-1-8-new-date-bug/
Apply the module found here: http://www.multibyte.at/wp-content/uploads/2013/10/Multibyte_DateFix.zip
After uploading, flushing cache and logout / login the problem is fixed.