Using a Export DataSource on a InfoCube with both compressed and uncompressed data. Which tabel does it use? Is it able to find data in both F and E tables?
usually the FM 'RSDRI_INFOPROV_READ' is used to read data from a provider...normally, every linked tables is read to extract all the necessary data...however I suggest you to do a 'little tour' in the OSS Notes 'cause in this situation some problems can occur (e.g. refer to 783831 'No data when reading using RSDRI_INFOPROV_READ' or 566762 'BW 30B: DataMarts for stock cubes').
Hope it helps (and, if yes, don't forget to assign some points...)