According to what you wrote it looks like that this is indeed an issue of new version of UC.
But you should verify it by looking in Windows task manager how much free RAM you have on starting UC and how much free RAM is available after a compare which fails.
Also when have you last time used the Windows disk cleanup tool in Accessories - System Tools to clean the folder for temporary files (and other files and folders which can be safely deleted)?
You can clean the folders for temporary files also manually by
- restarting Windows to make sure that any silent security update, installation or uninstallation process with files currently in temporary files folder can finish,
- enter in address bar of Windows Explorer %TEMP% and hit key RETURN to open this folder (temporary files folder of the current user acccount),
- delete with Ctrl+A and Shift+Del all files and subdirectories in this folder with ignoring the temporary files currently opened by running applications which cannot be deleted,
- enter in address bar of Windows Explorer %windir%\Temp and hit key RETURN to open this folder (temporary files folder of the system acccount),
- delete with Ctrl+A and Shift+Del all files and subdirectories in this folder with ignoring the temporary files currently opened by running applications which cannot be deleted. You need administrator privileges to delete files and folders in %windir%\Temp.
The Windows disk cleanup tool deletes only the files and subfolders in %TEMP%
older than 7 days and does not delete anything in %windir%\Temp
as non administrator user accounts do not have the permissions to delete files and folders in the TEMP subdirectory of the Window directory.
More than 2 GB of RAM can be used only by 64-bit applications (which often must be additionally written to use so much RAM at the same time). UltraCompare is a 32-bit application and therefore can use just up to 2 GB. And the total amount of free memory does nothing state about largest continous free memory block. Let's say there is in total 4 GB of free memory, but an application needs a 200 MB memory block, it can easily happen that the operating system returns to the application that there is no free memory for 200 MB because the entire RAM is used fragmented. In such situations users often wonder why a program fails to allocate memory although according to task manager there is enough free memory. What the user does not see in task manager is the memory fragmentation.
And all free RAM does not help if an application needs too many system resources. Windows cannot handle an unlimited number of system resources. Some articles about Windows memory management:
I suggest to run compares on large files with thousands or millions of differences without GUI as command line compare using the command line options
with the comparison results written to a file instead of displaying them for visual inspection. A visual inspection of the differences in GUI does not make much sense on large files with thousands of differences. Thousands of differences being inspected by human eyes is not really practicable, isn't it.