Cisco Switching/Routing :: 3750 - Error Message While IOS Upgrade

Have a small stack of two 3750 routers.  Get the following error message every few secounds:
 
%STACKMGR-4-STACK_LINK_CHANGE: Stack Port 1 Switch 1 has changed to state DOWN
%STACKMGR-4-STACK_LINK_CHANGE: Stack Port 1 Switch 1 has changed to state UP
 
Now I replaced the stacking cables but no joy. It was ok for an hr or so but then the error messages popped up again. Also random links on this stack back to access layer user switches have been going up and down randomly. So I have decided to take the next step and upgrade the IOS.
 
 Although when I try and copy a new IOS I get the following error:
 
%Error writing flash:/c3750-ipservicesk9-mz.122-55.SE6.bin (No space left on device)
 
Seems this image is 130MB while the image that is currently on it is 74MB and free space is 54MB. How do I get the image onto the router? If I delete the current image from flash will that cause the router to stop functioning?
 
Also I noticed there seems to be more than one flash directory. See below:
 
copy tftp: ?
  flash1:         Copy to flash1: file system
  flash2:         Copy to flash2: file system
  flash:          Copy to flash: file system
  null:           Copy to null: file system
  nvram:          Copy to nvram: file system
  running-config  Update (merge with) current system configuration
  startup-config  Copy to startup configuration
  system:         Copy to system: file system
  vb:             Copy to vb: file system
 
The current router image seems to be in flash1 and flash 2 also. Could I delete the image from flash1. Upload it there and then boot the router from flash1?