It means, typically, that the client or server is very busy. We would need a lot more information to give you any intelligent suggestions, but things to look at include:
- Server horsepower (RAM, CPU, memory, etc.)
- Client horsepower (ditto)
- Network speed (bandwidth, latency)
- Network quality (faulty network hardware, poor topology)
- Solution design (narrow vs. wide tables, use of themes instead of drawn objects, etc.)
- Server statistics (esp. wait time)
- Use of heavy unstored calculations
Typically, the behavior you're describing is an indicator that there's a communication issue. The client is trying to load data from the server (either because of user action or because of updates to the cache from the server). But there are potentially many reasons why it might be delayed; I've only given you some of them above.
Let us know more what your situation is and we can perhaps give you something more specific to look at.