It's probably some kind of automated error checking under
'tools'...options'...error checking.

Why would want to have the formula you have there?  Are you trying to add
the contents of A1 to .22?  (=A1+.22)

What is A1.22?  When I try it, I get a #NAME error.  This is just a guess
based on what I know could happen.  Is it possible you are entering
=sum(a1..a11) (notice the 2 dots.)  This is how you would enter a formula
using Lotus 123.  Excel recognizes this and allows it but changes it to the
format that it uses for the sum function; =sum(a1:a22)

Actually, I just tested and it also did it when I entered just one period.  
I.e. it changed =sum(a1.a22) to =sum(a1:a22).  I suspect it is for the same
reason, but do not have any proof.

When I used to use Lotus all those years ago, I always used two dots.  I
don't know what would happen using only one dot (especially with later
versions.)