You probably needed to replace the backup (PRAM) battery with a new one, not just pull the old one out and then put it back in. Depending on circumstances the expected lifespan of those batteries is between three and five years. A dead backup battery can produce exactly the symptoms you describe. Of course you have a fully stocked battery store right around the corner that is open 24x365 — NOT.
...using memory sticks because the CD drive/burner does not work
Given you already have at least one dead optical drive to contend with and the likelihood that more will partially or completely fail in the near future, given the age of your Macs, I recommend you discuss the possibility of getting an external optical drive with firewire and USB interfaces with your boss. They are relatively inexpensive and can save you a lot of time and difficulty.
I would also recommend a bootable external hard drive with USB and Firewire interfaces with OS X and a variety of troubleshooting and volume repair utilities installed on it to have handy in case of emergency. I have a bus powered 2.5 inch form factor enclosure with a 120 GB drive salvaged when I upgraded the drive in a laptop that I use. I don't have to use it often, but when I do it is absolutely invaluable. Besides emergency use it is a lot faster when I need to boot from an external volume to perform routine volume maintenance on hard drives.
Finally, I don't know about your side of the pond, but on our side I found a not great, but usable, set of micro-screwdrivers at the local hardware store for under $10 USD. Given what you are doing something like that can also be invaluable.
