NopCommerce 1.90 gives bad UPS Quotes
This post will give examples of bad calculations along with a link at the bottom for the corrected code. This information is provided for free, and I don't seek to recover money for the added benefit this provides your NOPCommerce 1.90 site; please do not assume that there is some type of warranty or guarantee that this will work; I encourage you to first deploy this in a test environment.
If you use the ups shipping module with NopCommerce 1.9, hopefully you've noticed that the shipping calculations are wrong if you ship more than one package.
It appears that the program logic used confuses UPS package requirements with shipment requirements, thus incorrectly calculating the dimensions it sends to UPS for a quote.
You can read up more on this issue at the NOPCommerce Forum http://www.nopcommerce.com/boards/t/4531/ups-shipping-calculation-issue-if-multiple-items-are-added-to-cart.aspx
Examples of Incorrect Shipping Calculations
One package of product A, shipping cost: $25.41
Two packages of product A, shipping cost: $122.61
Product A and Product B, shipping cost: $29.14
Product A and Two of Product B, shipping cost: $62.31
Examples of Correct Shipping Calculations
One package always gives the correct amount ($25.41).
Here, two of the same comes out to $27.82 (not $122.61).
Product A and B cost $39.32 (not $29.14)
One product A and two of B cost $64.73 (not $62.31).
The correct code and compiled DLL
Here is the UPSComputationMethod.cs file, if you have the source code, you can replace yours with this one and recompile.
If you don't have the source code version, here is the compiled DLL of Nop.Shipping.UPS.dll and the program debug database file (which i don't think you actually need) Nop.Shipping.UPS.pdb; There is a folder called BIN, make of copy of the current Nop.Shipping.UPS.dll (DO NOT LEAVE THE COPY IN THE BIN FOLDER AS THIS CAN CAUSE PROBLEMS) replace the Nop.Shipping.UPS.dll with the one you downloaded here, your website will automatically restart when it detects the new file. Test your shipping calculations to confirm they're correct.