Opening another workbook causes the currently opened workbook's formulas to calculate incorrectly

[nether]

I have a workbook that has a number of formulas and macros. Let's call this Workbook A. It works great until I open any other workbook. Let's call that Workbook B. Workbook B can be an .xlsx or .xlsm file. It does not matter which, but the formulas in Workbook A all get recalculated to the wrong values. I cannot figure out why it is doing this. Has anyone seen this? Does anyone have any suggestions on what the issue could be or have ideas of things I can try to fix it?

 

[nether]

I was able to resolve the issue. I was inadvertently disabling a UDF when the ActiveWorkbook name was not equivalent to Workbook A. This particular UDF is used in many other formulas and thus, everything was getting set to 0.