Ok there are a few problems here. One, you are limiting your cboLine to only show line items that have a match in your FLOC table but your cboLine is a combo box that is unbound which I assume means you're trying to use it to search for records.
So really you want your record source to be ALL possible lines so you can pick one of any of them.
You also have some weird lookup error going on because you have lookup fields on your tables, this is one of the main reasons I don't use them. If you get an error it's extremely hard to track down WHY it's occuring.
Here's what I would do
1. Delete both your cboLine and cboMachine
2. Create a new combo box (cboLine) with the following query as it's record source
Code:
SELECT LINE.LineID, LINE.[Line Name] FROM LINE ORDER BY LINE.[Line Name];
make the combo box have 2 columns, bound column is 1, column widths 0;2
3. Create a new combo box (cboMachine) with the following query as it's record source
Code:
SELECT MACHINE.MachineID, MACHINE.[Machine Name] FROM MACHINE ORDER BY MACHINE.[Machine Name];
make the combo box have 2 columns, bound column is 1, column widths 0;2
4. in the ON EXIT property of each combo box have (or if you prefer in your afterupdate event)
cboFloc.requery
From there you shouldn't have any problem with your cboFloc combo box.
I'm almost 100% sure you're encountering an artifact error because you're using a table that has a lookup value for a field (I've had this problem before using other people's tables). Compacting/Repairing won't fix the problem either you basically have to reformulate the parts that aren't working.