Like Jim said it's hard without knowing the details, on the other hand there are some general considerations to take into account, you should always make sure your client, boss, or end user understands the development cycle, if they ask you to develop in a month, something that normally would take 6 months, it's up to you to say yes or no, just because you can pull it off doesn't mean you should, by accepting your setting a standard for future projects, I know it's hard to do that as an employee, so if you have to do it, you should aim for a very simple application that does the job without any bells and whistles, always giving priority to the integrity of the data, function over feature. Using a framework, yours or a commercial one, is also a great advantage.

Now, focusing more on your specific problem, you could have validated your database, packed and reindexed your tables, just to get that out of the way, the next step I would take is debugging step by step, when the line with the error is reached, I'd look at the values of the expressions involved, this might sound obvious but sometimes we make wrong assumptions about where the error is generated.

Another possible cause could be a field named superid with a non character value, my way of dealing with this is using naming conventions, this keeps me from ever having variable names and field names with the same name, but then again, this are just shots in the dark without having more details, anyway good luck.