HP200LX version of 123 seems to be partially Y2K compliant. It doesn't like inputting dates as dd/mm/yy or whatever - you have to use 123 version 4 or above for this, I think. You have to use the @date function, which counts forward from 1 Jan 1900.
On my LX in Lotus:
1/3/2002 returns a fraction 0.0001665002...
@date(2002,1,3) returns ERR
@date(102,1,3) returns 37259, the date number for 3 Jan 2002. Format this as usual to get it to echo the date - "Lotus Standard Long Form" will echo as 03-Jan-2002 (UK style).
@date(2,1,3) returns 734. This is the date number for 3 Jan 1902, and may work for you or not depending on what you want to do. If you format the cell to "Lotus Standard Long Form" it will echo 03-Jan-02
If you get ***** make the column wider - Lotus must echo years from 2000 on as 4 digits, even though it echoes dates up to 1999 as 2 digits.
In other applications, the (Fn-,) shortcut works fine, although on my machine it generates a date field in dd-mm-yy format (two digits only for the year).
Can't see why backing up the machine should cause a fault with Lotus - it's burnt in to the chip and should not be capable of being overwritten.
Hope this helps.