Run Time error - 3001

[Timtropolis]

Greetings folks,

I am currently running some DAO code in one of my modules (Acc2k) that updates information in one table (rst1) with information from a lookup table(rst2). The code works fine (I've used it before with no problems) but I've been getting an error that I can't understand as to why I'm getting it. I've pasted the area of code below.

If RST1.[Billable_Product_Total] < rst2![upper limit] Then
With RST1
.Edit
!cs_order = rst2!order
.Update
rst2.MoveFirst
End With
Exit Do
End If


I am getting a Run time error - 3001, Invalid argument on the item highighted in bold. Basicially I'm scrollling thru about 170K records and all is going fine and then this error pops up. I have no clue as to why since it goes thru about 80% of the records with no problem. It also doens't popup on the same record all the time either, so that eliminates a bogus record. From what I can see, there are no issues with the records/data in the table being updated and vice versa.

Any ideas?

TIA,
Timtropolis