If you are facing the installation failure when downloading/updating from market, the reason can be that your card has been corrupted. It usually happens when you eject the card without unmounting it from the software(mobile or pc).
To confirm this, try manually installing an app and tell me if installation is successful or not.
Samsung GT-S5830 Galaxy Ace
ROM: AOKP 4.2.2
Scripts: CronMod INT2EXT4+
245MHz - 800MHz, SmartassH3