Version:           1.5.2 (using KDE KDE 3.5.4)
Installed from:    Slackware Packages
OS:                Linux

If I enter

A1=5
B1=7
A2=if(A1!=B1;"Not Equal";"Equal")

The result gives "Equal" for whatever values are in A1 if B1 is populated. If B1 is empty the result is always "Not Equal" for all values in A1. The reason for this is the ! of != becomes part of the cell reference for some reason, so it is comparing 'A1!' to 'B1' (in fact it probably isn't even comparing them. In the formula, 'A1!' is red and 'B1' is blue, but the cell B1 has a red box around it, and the cell A1 has no box)

If you then copy and paste this from A2 to B2 it changes the formula thusly

B2=if(A1!=C1;"Not Equal";"Equal")

The results are always "Equal" for all values in A1 (Or B1) when C1 is populated. If C1 is empty, all values in A1 (or B1) give "Not Equal"

Or copy from A2 to A3 the formula changes thusly

A3=if(A1!=B2;"Not Equal";"Equal")

The results are always "Equal" for all values in A1 (or A2) when B2 is populated. If B2 is empty, all vaules in A1 (or A2) give "Not Equal"

Also, if using absolute cell reference (ie A2=if($A$1!=B2;"Not Equal";"Equal") the formula will not copy to another cell, and is replaced with an error message: #### REFERENCE TO COLUMN OR ROW IS OUT OF RANGE

There seems to be a problem with the formula engine which is not tokenizing (?) the != properly. 

For all examples above the alternative operator '<>' works as expected, and copy and paste results in formulas which are updated correctly in the destination cells.

The manual says that != is a value operator for "not equals" and that <> is a valid alternative oerator.