A few things to try:
1. Are you using the same copy of the system software on all startup devices? There is always a chance you could have a corrupt System file. Try using a different floppy to boot the Plus or attempt to use the disks in question to boot another Mac. Questionable System files are by far the most common cause of this problem, followed by bad disks. Trying them in another Mac will tell you if this is an issue or not. Also, make certain there is a valid Finder file in the System Folder.
2. If you've eliminated the disk and System file as a culprit, look to see if there are any INITs or cdevs installed in the System Folder. A corrupt or incompatible INIT or cdev may cause a freeze.
1. Are you using the same copy of the system software on all startup devices? There is always a chance you could have a corrupt System file. Try using a different floppy to boot the Plus or attempt to use the disks in question to boot another Mac. Questionable System files are by far the most common cause of this problem, followed by bad disks. Trying them in another Mac will tell you if this is an issue or not. Also, make certain there is a valid Finder file in the System Folder.
2. If you've eliminated the disk and System file as a culprit, look to see if there are any INITs or cdevs installed in the System Folder. A corrupt or incompatible INIT or cdev may cause a freeze.