So far (only 15 mins!), I now have Mercury 4.8 back up and running with no errors.
I tried a number of things .... turned off Windows Firewall, stopped initiation of my antivirus, started with a Clean Boot, all without success.
Each day I automatically save a copy of the complete Mercury folder and an image of the system disk,.to a separate drive. I also have a copy of my previous Mercury (4.74) installation on this backup drive. So, I copied the 4.74 Mercury backup onto the system disk and ran its mercury.exe. It seemed to work without any errors.
Given the success with 4.74, I decided to re-install 4.80 on top of the existing 4.80. I wasn't sure that I could do this, as I wasn't upgrading to a new version. There were no complaints from Mercury about this not being an upgrade and the new install finished successfully. On starting the new 4.80 everything seemed to start normally with no BEX errors.
So, I don't know what happened, Maybe something became corrupted in the previous copy of 4.80. The disk where the Mercury folder exists is monitored for its health and it is reporting 100% good, so I don't think that the disk is starting to fail.
Anyway, I am pleased to be back up and running again and will monitor the situation.
I don't know whether it is anything to do with what happened, but a folder has appears in the root of the system disk named BAD-16-06-24.1243. It is an empty folder but it seems to be suspiciously named with the date and time when Mercury started to fail.
Thank to all who tried to help me!
Gordon
<p>So far (only&nbsp;15 mins!), I now have Mercury 4.8 back up and running with no errors.</p><p>I tried a number of things .... turned off Windows Firewall,&nbsp;stopped initiation of my antivirus, started with a Clean Boot,&nbsp;all without success.</p><p>Each day I automatically save a copy of the complete&nbsp;Mercury folder and an image of the system disk,.to a separate drive.&nbsp; I also have a copy of my previous Mercury (4.74) installation on this backup drive.&nbsp; So, I copied the 4.74 Mercury backup onto the system disk and ran its mercury.exe.&nbsp; It seemed to work without any errors.</p><p>Given the success with 4.74, I decided to re-install 4.80 on top of the existing 4.80.&nbsp; I wasn't sure that I could do this, as I wasn't upgrading to a new&nbsp;version.&nbsp; There were no complaints from Mercury about this not being an upgrade and the new install finished successfully.&nbsp; On starting the new 4.80 everything seemed to start normally with no BEX errors.</p><p>So, I don't know what happened,&nbsp; Maybe something became corrupted in the previous copy of 4.80.&nbsp; The disk where the Mercury folder exists is monitored for its health and it is reporting 100% good, so I don't think that the disk is starting to fail.</p><p>Anyway, I am&nbsp;pleased to be back up and running again and will monitor the situation.</p><p>I don't know whether it is anything to do with what happened, but a folder has appears&nbsp;in the root of the system disk named BAD-16-06-24.1243.&nbsp; It is an empty folder but it seems to be suspiciously named with the date and time when Mercury started to fail.</p><p>Thank&nbsp;to all who tried to help me!</p><p>Gordon&nbsp;</p>