NO FUEL in 737NG

Hi,I have the 737NG installed (all configs from 600 to 900) and since recently, whatever fuel quantity I load in the plane, fuel will remain at zero on the MFD and in the FMC. My config is FS 9.0 (French - unpatched) and used to run perfectly for a long time. Some time ago, I moved this FS9.0 from its location to another directory in "Program Files" and installed FS9.1 (English, patched) in Program Files/Microsoft Games/ and this runs perfectly. Just to be sure, I uninstalled 737NG from my FS9.0 directory (using the PMDG uninstall tool) and then re-installed in the same place. Same problem : I still have the same problem (no fuel in the FS9.0 version - no problem in the FS9.1) which is strange since both run from the same fs9.cfg file. I have checked and compared the .air and aircraft.cfg files in both installations and they are OK. I have a few add-on aircraft installed (mainly Eaglesoft) but they are present in both configs.I really would appreciate some help on this one. Thanks in advance. Bruno DUPRE