From the manufacturer:
Legacy Spectra Geospatial GNSS Receiver Firmware Upgrades
Recently, there have received reports of positioning issues with the ProMark 500 encountering an inability to report a position. This is caused by the GLONASS almanac providing out-of-tolerance data for one of the GLONASS satellites. The positioning engine in the receiver treats the almanac as accurate.
This issue has been resolved with the firmware fix which you can download through the link below. This should be distributed immediately to all affected users, as it will resolve the issue with the GLONASS almanac.
I have had numerous calls from users having installation problems with the new firmware over the past week.
I believe this has been due to partial downloads. If you have issues, please use the .ZIP mirrored downloads that I have placed in this web location:
After downloading the ZIP file, unzip to obtain the factory binary file.
Hopefully this is the last update with respect to this issue. (Although I am left wondering about the ProFlex 500 which has not had any new firmware releases.)