Hi,
This looks like an out of memory error with a 32-bit version of PixInsight running on a 32-bit operating system. Please note that all 32-bit versions are now
officially obsolete. If you are working with 1GB files, then I strongly recommend you use a 64-bit version of PixInsight on a 64-bit operating system. Otherwise, if you describe some of the operations you want to perform, I can try to find some workarounds to avoid or alleviate out of memory problems.
The startup error is unrelated to the other issues and is probably due to a brief server downtime or a network error, which may have caused problems to authenticate your trial license. These are temporary connection problems that happen from time to time. Once the application starts, it will run normally.
As for the problem with Windows Explorer, we are not responsible for issues caused by third-party applications that are unrelated to PixInsight. These errors are probably caused by your system running at the limit of memory resources. Again, the best way to fix them is using 64-bit software.