Error - default image may not be modified. Use the i-/image flag instead.

[Anonymous]

Hi, I'm a student and I have to submit a short Maya Animation in 2 weeks and I would really appreciate if someone could help me. Thank you in advance. 

I rigged my model and then I bound the skin to the skeleton and then I painted skin weights and when I wanted to reopen the file it takes very long and an error occurs:  default image may not be modified. Use the i-/image flag instead. 

I tried to change the prefs file name to prefsOld but it doesn't help. 

Does anyone have a solution how I could fix this? Thank you so much.