the drivers work for two years, and didn't brake yesterday. drivers are always ok as read only files. seems like hardware problem of the sound card. but before say this, try to plug it on another pci slot, and try to reinstall the drivers again.
also a complete reinstall of your operating system might help. maybe there is a conflict with other hardware or drivers. go step by step install - check - install - check (one installation at a time) to see when the problems start, so you can understand what is the fault.
if the above don't help, this is problematic sound card for sure. then try another cheap sound card just to see if works ok.