Data Protector CRS operation cannot be performed in full-screen mode

Today's head-scratcher: after upgrading to 9.07 on a Windows cell manager, the CRS service won't start.

Eventvwr says something even weirder:

The Data Protector CRS service terminated with service-specific error The requested operation cannot be performed in full-screen mode.. 

I was in full screen mode at the time, but it still wouldn't start even when I minimised my RDP session. For my own sanity, I was glad of this.

Trawling through Daniel Braun's http://www.data-protector.org blog, I saw some comments there that it could be related to anti-virus software. Nope, not that either.

The debug.log said something a little bit more believable:

[SmCreateTable] MapViewOfFile(size:17505216) failed, error=[5] Access is denied.

I discovered that I could reliably get that message added that message every time I tried to start the CRS. But what is actually being denied?

So I ran omnisv start -debug 1-500 crm-vexatious.txt

I then had a 160KB file created in C:\programdata\omniback\tmp that began with OB2DBG, ended with crm-vexatious.txt and had CRM in the filename. Good: at least it gets far enough that it can create debug messages.

Scrollling right to the bottom of it, there it was:

Code is:1007  SystemErr: [5] Access is denied
************************   DEFAULT ERROR REPORT   ***************
[Critical] From CRS@cellmgr.ifost.org.au "" Time: 5/8/2016 1:00:33PM
Unable to allocate shared memory: Unknown internal error.

Internally, the function to return a shared memory segement presumably encodes something as 1007; CRS then exits with that code (which is the standard Windows error code for "can't be performed in full-screen mode").

There aren't many reasons for a shared memory allocation to fail. In fact, the only one I can think of that could be relevant here is if the segment already exists. I thought about figuring out what the equivalent to ipcrm is on Windows, gave up and rebooted the box.

And it came up perfectly. Funnily enough, if I had had no idea what I was doing, I would have just bounced the box to see if it would have fixed it, and saved myself a headache and some stress wondering what was going on. Ignorance would have been bliss.