Gift certificate calculation error -> double valuations

I'm getting serious errors in totals when using Gift Certificates:

Products in shopping cart: $45
tax (6%): 2.70
shipping: $1.30
subtotal: $49
Applied gift certificate: $10
total: $75.30

It apparently doubles the gift certificate value and adds the products in shopping cart total + shipping to come up with $75.30.

Am I missing something?

The GC module is configured as:
Gift Certificates

This module is installed
true

Sort Order
840

Queue Purchases
true

Include Shipping
true

Include Tax
true

Re-calculate Tax
None

Tax Class
--none--

Credit including Tax
false

Set Order Status
default

Thanks for your help!
-Peter

I too am getting INCORRECT gift certificate calculations:

Sub-Total: $85.00
Florida State Sales Tax - 6.00%: $5.10
Gift Certificates: $-15.00
Total: $145.10

What should occur is $85.00 + $5.10 = $90.10 - $15.00 = $75.10.

However, It appears as if the gift cert module is doing the calculation, the adding $70.00 (which is $85.00 - $15.00 gift cert).

I am using Zen-Cart 1.3.8. Is this a bug?? If so, how do I correct it? Also, it appears 1.3.8a is out? Does this fix this issue? I can't seem to find what 1.3.8a does above 1.3.8.

My Gift Cert Module Config is the default:

Gift Certificates

This module is installed
true

Sort Order
840

Queue Purchases
true

Include Shipping
true

Include Tax
true

Re-calculate Tax
None

Tax Class
--none--

Credit including Tax
false

Set Order Status
default

A quick response would be appreciated! Thanks!

Bob

Bug Fix for the Gift Certificate error when taxes are on is at:
http://www.zen-cart.com/forum/showthread.php?t=83928