probably
If you move to europe, you will probably find your residence interrupted if you are over there and employed more than 6 months, in addition, you will find your residence interrupted if you are over there and employed more than 12 months...
Potential questions: did you pay US taxes on the income generated overseas? If not, you will probably be deemed to have established new residence overseas even if you get to keep your GC. Did you apply for Re-entry permit (for stay over 12 months)? Did you buy a house overseas? did you maintain your house/apartment here in the US? How long was the assignment: couple of weeks, couple of months, couple of years??? was this to your home country? did you bring your family?
If your employer is religious organization, you might apply for "retention of residence for naturalization" (form on ins website) prior to leaving US.
Your stay in Europe could also impact on need for police clearance for your residence period over there...
