Basically, you cleared out your system's memory by restarting your computer. This allows for dead processes to clear the queue, their memory footprint to become zero, and return that used memory to the available pool.
You may have had a few programs running at the time. I prefer not to use HP's software; I am of the opinion that it is bloated and such. I just download the basic driver package (13.8mb -- there is still some extra crap) and use that. Software is useful, however, if you do a little bit of photo editing. If you do a lot of editing photos, the bundled software is worthless. Other stuff included is free trials for crap (AOL comes to mind) and other junk.
But that is my view on the situation, and if you have a very important document that must be printed, save the current version, restart the computer, and print it then; this gives the computer and printer the ability to print the documents.
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If you are technically inclined, of which I pass no judgments about, continue reading. If you do not feel up to the task, you may stop here, and it will not hurt my feelings.
Basically, to print a document, a few steps have to occur:
1 - The document must be present in memory. This is usually where it is loaded into the document editing program, such as Microsoft Word.
2 - The editing program must have access to the printer, which is usually granted behind the scenes.
3 - The editing program must understand the language of the printer. It must take the document, and convert it into a language that the printer understands. This step is where many "out of memory" issues occur, where the symptom is an incomplete printout of the document.
4 - The editing program sends the translated document to a printer queue. This is where printing jobs are held before they are printed. Sometimes, the administrator halts the queue, whether for maintenance or other reason. Usually, it is as simple as making a technology support call, or resuming the printer queue.
5 - The printer reads the queue, and selects the print job to process.
6 - The printer prints the print job, and out comes the document.
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Simplification of many concepts, which can be quite technical, to where even I get lost, or lose interest.
