That's a common error when GPS freezes up, or you close out of the collection software without exiting. It also happens if you power off the GPS without exiting collection software. I usually have to open a trouble ticket and send the file to Trimble to have it processed.
Thanks for your reply! Unfortunately, that does not seem to be the problem in my case. I just collected some data in a new shapefile and made absolutely sure to close all the software -- still nothing.
Although this time the initial error message is simply "Invalid data file. Cannot open file." without mentioning a bad time period.
CheckSSF still gives the same output as above (barring obvious differences in the time of collection).