Craig - I assume that you have just done the 1.7 to 1.8 upgrade.

I just compared the 1.7 and 1.8 act.customerEstimationItem archetypes, and yes there are now some 'cannot be negative' assertions.

I must admit that we also use the 'not kosher' products with negative prices that are discounts, and thus the following (which would work under 1.7) now causes an error:

The "fix" is to remove the 'not negative' assertion in the archetype.  ie use Administration|Achetypes to edit act.customerEstimationItem as follows:

just delete the nonNegative assertions against the fixedPrice, the highTotal, the highUnitPrice, and the lowTotal and lowUnitPrice.

Note that as http://www.openvpms.org/documentation/csh/1.8/admin/archetype says: "Note that if you are modifying archetypes, then although you can do it directly by editing it on the screen, it is best to edit the adl file, and then import it. This has two advantages. Firstly you have a copy of the modified archetype that can be re-used if/when the system is upgraded. Secondly, if you are adding a new field (more correctly referred to as a node), then you can control where it is displayed because, in general, the screen layout is determined by the order of the nodes in the archetype."

Regards, Tim G