UG part Open error

Hello Viewers,

Plz, go through the attached image,

I suffered a lot from this error,
I have created some models in UG NX3 with or without drafting, when i open it within 1-2 weeks duration (after completion) it opens & work nicely,
but when i open the same parts after 3-4 weeks(after completion) it will give me the error (as attached the image), & i am unable to open it,

Does anyone have any idea why this is happening?
It will be very greatful if anyone give me solution for it.

[andrewyipko]

Were you using a legal license to create the file?