There is a serious disk error on file ~Word Work File S{A1F41F30-FB84-B649-9F8A-F0A7D2698BBF}.tmp

its completely changed my opinion of Microsoft and Apple being reliable software producers.

I run literally dozens of various programs on my Mac, including three other Word Processors.  Microsoft's products are the only ones that have these problems.

A moment's thought will make clear that a problem that affects every app is likely a problem with your OS (or hardware), but a problem that affects only a single app is almost certainly the fault of the publisher of that app.

(In this case two apps are affected, but they both use the same code for text editing.)

While you're waiting for Microsoft to fix this, allow me to suggest you give Pages a try.  It comes free on every Mac, and definitely has my favorite UI of any Mac word processor.  Pages is not my first choice for lengthy complex documents like dissertations, but I wrote plenty of term papers, some up to 50 pages, with footnotes, charts and tables and other graphics, and it worked very reliably.

Other Mac Word Processors I use and like include Mellel and Nisus Writer Pro.  In the past I've also used Mariner Write, thought I haven't tried it in a few years.  You might also take a look at Bean and Scrivener, both of which are well reviewed (though I haven't tried either).

I'm perfectly happy with my Mac, and I was perfectly happy with Word until they introduced this bug.  In Microsoft's defense, it's obviously an obscure bug or it would have shown up in testing.  (They do test these things, you know.)

I mostly encounter the bug in Outlook (because it uses the same editing code as Word), but that won't be a problem much longer because my company is switching to gmail.  (And finally all our Mac and Windows users will have feature parity!)

Still, I need (and want) to be able to use Microsoft Word for a long time to come, so I hope they'll fix this soon.  (And I'm helping to narrow it down by collecting logs for them.)

1. MS Office 2011 did not solve the problem for me - this entire issue (all the errors, need to "save as" all the time," etc. ) startedless than an hourof having installed El Capitan (the newest Mac OS X) when it came out last fall. And I had Office 2011 for Mac at the time. I ONLY bought Office for Mac 2016 in the hope of resolving the problem, which it obviously did not.
2. I failed to mention in my original post that not only do I get "there is a serious disk error..." messages constantly, I also get the following messages constantly: 

• "Word could not create the work file. Check the amount of disk space on your startup disk." (Even though I have plenty of disk space)
• "Word cannot save or create this file. The disk may be full or write protected..." It is neither.
• I haven't saved the related error message, but half the time I can't even open a Word file until after trying multiple times. 

3. Re Steven-NAB-Klein's post re losing his material - I'm no technical expert, but :

• if you have multiple backups (Time Capsule does this), you shouldn't have to go too far back before finding a non-corrupted version.
• going forward, use cloud backup solution as well, which will do automatic backups quite often. 

Both of these solutions have worked well for me as a workaround from consequences of this massively pathetic incompatibility issue.

They also served as a complete miracle several years ago when I was traveling abroad and lost my computer -- and my entire livelihood depends on my it. Backup backup backup every way you can. Cloud backup providers are cheap and an important duplicate solution.

Many thanks for your response.  Indeed I also have faults on Pages which even the mac techs can't figure out.  I have reinstalled the OS a couple of months ago. Safari is also a hard task master so overall not a happy experience.

I am happy using google docs at the moment.

I am fully aware that things get tested but having done a few contracts in IT (as a non-tech), so I can feel rather safe in presuming that the release went ahead with known issues and that given the percentage of people of effected (with no impact on the bottom line) will not be scoring a high issue rating.

The number of releases I know are just fixes and the pressure to get out to market far outweighs any interest in consumer impact - as long as the thing generally works with a percentage pass rate - the next release will simply be a suite of fixes.

In my mind apple does not have comparable software - in all my working life I have never seen any doc written in pages.  And as said, pages has proven very unstable for me - won't even do automatic numbering which is a rather simple editing task.

So a big no to both and won't be even considering any apple allied products.  I like the interface and was in the begining going to get an iphone but after the debacle of buying this laptop, the poor customer support, the ridiculous issues with safari and pages, and the absolutely negliglible decision to go to market with the el capitan in which this would have been a known issue - I'm done.  Going back to PC - which I would rather not - but have a life to live!

And it won't be a quiet change back.