Hm, this happens all the time? I can think of an incomplete installation, or that you try to open openLCA several times at once, or that you have allocated too much memory, more than your computer has.
By default, we set the memory to 3.6 GB, if your computer has less, then you can change it in the openLCA.ini file, which is in the same directory as openLCA.exe; find the line -Xmx3584M, this is the allocated memory in megabyte (3584). Change it to a lower number, save the file and try to restart.
Or as very first step, just retry the installation, easiest via the zip files.