In previous versions we have run price reduction promotions for products (for example $5 off a product) by adding a new product which has a fixed price of -$5. Then when we charge for the product we also charge the extra product which is -$5 and the total invoice price would be $5 off. 

I like doing it this way as I can then run a report to list the sales of the discount to claim rebates back.

In 1.5 this doesn't seem to be working. When the item is charged the fixed price is charged as $0. When I just tried I was able to change the fixed price to -$5 but during the last week when it has happened we haven't been able to get it changed to a negative value. I'm not sure what it is that we had done differently. 

Is there any reason that the behaviour has changed?

Related to this issue, I now have an account that has had a counter sale done (selling the actual product) and then 2 subsequent counter sales. The second counter sale has a $5 discount on the '$5 off product' so it has a total invoice price of -$5. Then there is a third counter sale which has a unit price on the '$5 off product' of -$5 and a total invoice price of -$5. The account should be in credit for $10 but is showing a 0 balance. 

If I check the account I get this message:

 Mismatch in Customer Account Balance.
Expected an Account Balance of ($10.00), but current Account Balance is $0.00.
Regenerate balance?

If I then press OK to regenerate the balance it is still $0.

I'm not sure what's going on here or how to correct it. In the end we need to end up with account balance of $5 credit because the client didn't receive her $5 off ie. she paid full price. 

Hope that all makes sense,

Matt Y