I just posted this elsewhere - a fix, I think.
I found the answer to the USPS issue by talking to a really technically competent person at USPS>
At the moment, Safari does not work. Use Firefox.
Here is what you need to do:
1. Be sure you have the latest version of Adobe reader installed (and only one). Open reader. Go to preferences>internet. Unclick +"display PDF in browser using"+
2. Open Firefox>preferences>applications. Scroll down to PDF file. The window should show Adobe reader. If it has "default" after Adobe reader, select other and then select Adobe reader from the options. Close the preferences.
3. Go to the USPS site and try to print a sample label.
This worked for me.
We had click and ship working for several months without problems. It was even working after the snowleopard upgrade. But since the subsequent security update that included an HP driver update click and ship is not working in Safari. (When you click to print nothing apparently happens).
The solution for now is to use Firefox. When you click you'll get a message asking you what to do with the serverlet download. You can select having it open in adobe reader in which case it will open automatically and print or you can save it to disk. If you save it to disk you must rename the file so that the extension is .pdf
I have used click n ship for a long time and have had this problem at other upgrades but always made it work again. This time I am stymied. Tried removing pdf plugin and all other suggestions without results. Bottom line, can't use click n ship on safari in snow leopard. Of course it is possible to open the file by going to window, activity and clicking on the file itself after it loads. Hope this gets fixed soon. Hate having to use different browsers for different things. Also even when the pdf plugin is in the internet plugins folder it doesn't show up in loaded plugins in Safari.
I tried what Barry without success. But, I ended up able to print labels because of his suggestion.
I went to Adobe Reader preferences>internet and unclicked "display PDF in browser using" just as he advised.
But when I went to Firefox>preferences>applications, I couldn't select Adobe Reader from the options. I could navigate to it, but the selection wouldn't stick.
I tried to print test labels again, with no success.
Later I noticed my downloads folder had several files named com.usps.cns.web.pdf.LabelGenerationServlet. They were the test labels I had tried to print.
I checked back in Firefox>preferences>applications and saw that PDF file was set for Save File.
Just delete the LabelGenerationServlet extension and Preview will open them.
I then went back to the USPS site and printed my label. I kept the USPS page open. I then opened the file in my Downloads folder and printed the label using Preview. Only then did I click on the appropriate button on the USPS page to signify the label printed successfully.
1. Go to Adobe Reader preferences>internet and unclick "display PDF in browser using"
2. In Firefox>preferences>applications set PDF file to Save File
3. Print a test label. Keep the USPS page open.
4. Open your Downloads Folder and delete the LabelGenerationServlet extension from the com.usps.cns.web.pdf.LabelGenerationServlet file you'll find there.
5. Test to make sure you can print it.
6. Now print your label. Again keep the USPS page open, DON'T click on anything in it yet.
7. Follow steps 4 and 5.
8. If successful, click on the appropriate button on the USPS page.
It's a few hoops to jump through, but it worked for me.
To be able to print out USPS.com postage, Safari's build in PDF viewer is the root of the problem and must be turned off. This can be done in one of two ways.
1) Use a program like Cocktail to turn off PDF viewing in Safari. In Cocktail , this option is labeled "Disable PDF Support".
2) Do an Internet search for "Disable Safari PDF Viewing" and find the terminal command that does the same thing.
After doing either, Restart Safari. The display of the PDF file now happens in Preview and can be printed from there.
I'm having an awful time of this. I used to have no problems printing these labels; after upgrading to Snow Leopard I had to switch to Firefox, but last week that stopped working. Following instructions in a discussion on another site, I used Opera last week, which worked. But now nothing works. I've spent an hour painstakingly trying all of the fixes in this discussion, but I cannot get to the print dialog box-- the USPS site stays stuck in "processing". I also spent time on and email chat box with a USPS rep but he had nothing to tell me (he thought "snow leopard" was a kind of browser. Very disappointed because I've been relying on this service to save a tone of time at the post office.