This is almost certainly a problem with the .jou file (the 'journal' file). When running a script or testplan, silktest logs the results to the journal initially, then constructs the results file from the journal after the run has finished.
When you open a results file in silktest, it first checks to see if there is an associated journal file; if there is, then it opens the journal, extracts the latest results from there, and puts them in the results file before showing it to you. If the journal has become corrupted (can happen if silktest crashes out half-way through test execution for example) then it might not be able to open the journal, and fail to open the results file at all.
The only solution to this kind of situation is to go and delete the journal file. A bit extreme (you lose all the results from your last run) but it works.