Error message when loading project

[franceint]

Between yesterday, when my project was working, and today, when I tried to load it, something happened. Now when I try to display one of the forms, I get the following error message:

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To prevent possible data loss before loading the designer, the following error must be resolved:

Value cannot be null. Parameter name: objectType

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So what does this mean and what can I do about it?

[jmcilhinney]

The error message means that a method is being called and Nothing is being passed to its objectType parameter and that is not allowed. More than that we can't really say because we have no idea what method. You'd need to check out the exception's stack trace to see where the exception is being thrown. It may be that something is corrupt, either in your project or in your system but, from the available information, it's not possible to know. If other projects are OK then it's more likely to be the project rather than the system.