I ran into the following the hard way recently. Since I don't trust anybody's tech support to actually test new service packs or publish known issues, I figured I'd mention it here: SP1 for SBS 2003 breaks Aladdin NetHASP, and programs which use it.
NetHASP is 3rd-party software which programs use to tie software licenses to a physical dongle (known as a "hasp" or "sim"). In my case, our client was using SigmaTek's SigmaNest and Develop programs (line-of-business stuff), we had the Network sim plugged into the SBS box and the NetHASP License Manager program running on it. After the upgrade to SP1, SigmaNest on all workstations could no longer find the Network Sim, and would not run.
Anyway, judging by known issues I'd read about, I pursued a firewall angle. I found out what port the NetHASP connection uses (475), and made sure workstations could see that on the server (they could). I reinstalled the NetHASP License Manager. I reinstalled SigmaNest. Nothing worked.
Finally, dreading a bad support like I've had all too often, I caved and called SigmaTek support. After an hour on the phone with a well-intentioned, but lower-level support employee, he finally contacted Aladdin support (at my suggestion). Eventually he got hold of them and the three of us worked together on it for a good while. Eventually we tried a new (command-line) version of the NetHASP License Manager driver, and voila! it worked again.
For the record, we had purposely waited a month after SP1's release to let any kinks get worked out (or at least known). I'd also immediately mentioned the SP1 install to both SigmaTek and Aladdin's support reps, since it was a likely culprit. Seemingly neither had run into the issue.
Now, I'm not sure, but this suggests to me that neither company is proactively testing new Windows patches and service packs. If true, this is a very bad thing (if not, I'd love hear otherwise!). It's also possible that they did know, but simply hadn't communicated that info with their support reps (and certainly had not via their support websites).
I asked them to document what we'd found, but I don't have high hopes. So... hopefully this anecdote will help out some other poor NetHASP clod like me: get the new/other NetHASP driver, and push the vendors to publish the problem and solution.