Update: Dina Ezzat suggests the Egypt-Qatar rift is about Sudan/Darfur as well as the Palestinians:
The summit, however, is unlikely to escape being the scene of squabbles over managing the reconciliation process between the Darfur leaders and Al-Bashir's regime. While Qatar is determined to pursue earlier efforts to conclude a comprehensive peace deal on that front other Arab countries -- especially Egypt -- are determined to deny Doha control over the issue. As a result the summit may not issue a resolution with clear language on the Darfur-Khartoum reconciliation process.
The anticipated Egyptian-Qatari confrontation in Doha next week will not be confined to the management of the Darfur peace process. The diplomatic tug-of-war between the two countries that has continued for 12 months, especially over Palestinian reconciliation, is likely to cast a shadow across the Doha summit. With President Mubarak unlikely -- so far -- to attend, sending the foreign, or at best, prime minister, Qatar may not be so keen to avoid some squabbling over the text of resolutions to be adopted by the summit on the Palestinian issue. Sources say that Qatar has already suggested to several Arab countries that there is a need to break the "Egyptian monopoly" over Palestinian reconciliation. While this Qatari effort may not succeed -- as some Qatari officials acknowledge -- it would certainly impact on already tense Egyptian-Qatari relations.
Update II: AP has a write-up saying:
Hosni Mubarak's decision, which came two days before the summit starts, already throws major doubts on its chances for success as the organization's foreign ministers pleaded for unity in the face of threats against its members.